The pharmacology of progesterone , a progestogen medication and naturally occurring steroid hormone, concerns its pharmacodynamics, pharmacokinetics, and various routes of administration. [1] [2]
Progesterone is a naturally occurring and bioidentical progestogen, or an agonist of the progesterone receptor, the biological target of progestogens like endogenous progesterone. [1] Progesterone also has antimineralocorticoid and inhibitory neurosteroid activity, whereas it appears to have little or no glucocorticoid or antiandrogenic activity and has no androgenic activity. [1] Because of its progestogenic activity, progesterone has functional antiestrogenic effects in certain tissues such as the uterus, cervix, and vagina. [1] In addition, progesterone has antigonadotropic effects due to its progestogenic activity and can inhibit fertility and suppress sex hormone production. [1] Progesterone differs from progestins (synthetic progestogens) like medroxyprogesterone acetate and norethisterone, with implications for pharmacodynamics and pharmacokinetics as well as efficacy, tolerability, and safety. [1]
Progesterone can be taken by mouth, in through the vagina, and by injection into muscle or fat, among other routes. [1] A progesterone vaginal ring and progesterone intrauterine device are also available as pharmaceutical products. [3] [4]
Progesterone is a progestogen, or an agonist of the nuclear progesterone receptors (PRs), the PR-A, PR-B, and PR-C. [1] In one study, progesterone showed EC50 values of 7.7 nM for the human PR-A and 8.0 nM for the human PR-B. [5] In addition to the PRs, progesterone is an agonist of the membrane progesterone receptors (mPRs), including the mPRα, mPRβ, mPRγ, mPRδ, and mPRϵ. [6] [7] It is also a potent antimineralocorticoid (antagonist of the mineralocorticoid receptor (MR)), [8] [9] as well as a very weak glucocorticoid (agonist of the glucocorticoid receptor). [10] [11] Progesterone does not interact significantly with the androgen receptor (AR) or with the estrogen receptor (ER). [1] In addition to its activity as a steroid hormone, progesterone is a neurosteroid. [12] Specifically, it is an antagonist of the sigma σ1 receptor, [13] [14] a negative allosteric modulator of nicotinic acetylcholine receptors, [12] and, via its active metabolites allopregnanolone and pregnanolone, a potent positive allosteric modulator of the GABAA receptor, the major signaling receptor of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). [15]
Compound | PR | AR | ER | GR | MR | SHBG | CBG |
---|---|---|---|---|---|---|---|
Progesterone | 50 | 0 | 0 | 10 | 100 | 0 | 36 |
Notes: Values are percentages (%). Reference ligands (100%) were promegestone for the PR , metribolone for the AR , E2 for the ER , DEXA for the GR , aldosterone for the MR , DHT for SHBG , and cortisol for CBG . Sources: [1] |
Compound | Form | Dose for specific uses (mg) [lower-alpha 3] | DOA [lower-alpha 4] | |||
---|---|---|---|---|---|---|
TFD [lower-alpha 5] | POICD [lower-alpha 6] | CICD [lower-alpha 7] | ||||
Algestone acetophenide | Oil soln. | - | – | 75–150 | 14–32 d | |
Gestonorone caproate | Oil soln. | 25–50 | – | – | 8–13 d | |
Hydroxyprogest. acetate [lower-alpha 8] | Aq. susp. | 350 | – | – | 9–16 d | |
Hydroxyprogest. caproate | Oil soln. | 250–500 [lower-alpha 9] | – | 250–500 | 5–21 d | |
Medroxyprog. acetate | Aq. susp. | 50–100 | 150 | 25 | 14–50+ d | |
Megestrol acetate | Aq. susp. | - | – | 25 | >14 d | |
Norethisterone enanthate | Oil soln. | 100–200 | 200 | 50 | 11–52 d | |
Progesterone | Oil soln. | 200 [lower-alpha 9] | – | – | 2–6 d | |
Aq. soln. | ? | – | – | 1–2 d | ||
Aq. susp. | 50–200 | – | – | 7–14 d | ||
Notes and sources:
|
Progesterone is a potent antimineralocorticoid. [8] [9] [35] It has 1000% of the affinity of aldosterone, the major endogenous agonist, for the human MR, and 100% of the affinity of aldosterone for the rat MR. [36] [1] [8] Progesterone produces antimineralocorticoid effects such as natriuresis (excretion of sodium in the urine) at normal physiological concentrations. [9] A 200 mg dose of oral progesterone is considered to be approximately equivalent in antimineralocorticoid effect to a 25 to 50 mg dose of the potent antimineralocorticoid spironolactone, which itself is a derivative of progesterone. [37] Doses of progesterone of 50 to 200 mg by intramuscular injection, which are similar to progesterone exposure in the third trimester of pregnancy, have also been reported to produce antimineralocorticoid-like effects. [35] The antimineralocorticoid effects of progesterone underlie its ability to lower blood pressure and reduce water and salt retention and its potential application in the treatment of hypertension. [38] [1] [39] [35] An active metabolite of progesterone, 11-deoxycorticosterone (21-hydroxyprogesterone), is a precursor of aldosterone and has strong mineralocorticoid activity (i.e., is a strong agonist of the MR). [37] However, it is formed in relatively small amounts, and any such effects produced by it are usually outweighed by the antimineralocorticoid activity of progesterone. [37] Progesterone may be a relatively weak antimineralocorticoid in vivo. [40]
Progesterone is a partial agonist of the glucocorticoid receptor (GR). [1] [10] [11] [41] [42] It has about 35% of the affinity of dexamethasone, a corticosteroid, for the human GR, and about 3 to 11% of the affinity of dexamethasone for the rat GR. [36] However, progesterone appears to show weak or no glucocorticoid activity and no antiglucocorticoid activity in vitro and in animals. [42] Nonetheless, progesterone has been found to upregulate the thrombin receptor in vascular smooth muscle cells in vitro, a glucocorticoid effect, and this could have clinical relevance in relation to risk of blood clots. [1] [43]
Steroid | Class | TR (↑)a | GR (%)b |
---|---|---|---|
Dexamethasone | Corticosteroid | ++ | 100 |
Ethinylestradiol | Estrogen | – | 0 |
Etonogestrel | Progestin | + | 14 |
Gestodene | Progestin | + | 27 |
Levonorgestrel | Progestin | – | 1 |
Medroxyprogesterone acetate | Progestin | + | 29 |
Norethisterone | Progestin | – | 0 |
Norgestimate | Progestin | – | 1 |
Progesterone | Progestogen | + | 10 |
Footnotes:a = Thrombin receptor (TR) upregulation (↑) in vascular smooth muscle cells (VSMCs). b = RBA (%) for the glucocorticoid receptor (GR). Strength: – = No effect. + = Pronounced effect. ++ = Strong effect. Sources: [44] |
The binding and activity of progesterone at the androgen receptor (AR), the biological target of androgens like testosterone and dihydrotestosterone (DHT) in the body, is controversial. [45] Some studies have found progesterone to bind to the AR, with agonistic and antagonistic activity exerted, whereas other studies have found very low or no affinity for the AR at all. [45] In animal studies, no androgenic effects have been observed, but weak antiandrogenic effects have been reported. [45] The weak antiandrogenic activity has been attributed not to antagonism of the AR by progesterone, but rather to its weak 5α-reductase inhibition and consequent inhibition of the conversion of testosterone into the more potent DHT. [45] There is no clinical evidence of AR-mediated androgenic or antiandrogenic activity with progesterone. [45] Progesterone has not been associated with any classical androgenic effects in clinical studies in women, including no changes in the blood lipid profile or sex hormone-binding globulin levels, acne, oily skin, hirsutism, or voice deepening, nor with virilization of female fetuses. [46] [47] [48] [49] [50] As such, the scientific consensus is that progesterone is clinically neither androgenic nor antiandrogenic. [1] [51] [52] This is in contrast to many progestins, such as 19-nortestosterone derivatives (e.g., norethisterone, levonorgestrel, dienogest) and 17α-hydroxyprogesterone derivatives (e.g., cyproterone acetate, medroxyprogesterone acetate), which do bind to the AR and have been associated with significant androgenic or antiandrogenic effects depending on the progestin in question. [1] [52] Due to its lack of androgenic and antiandrogenic activity, and hence lack of masculinizing and feminizing effects, progesterone is one of the few progestogens that is suitable for use during pregnancy in women at risk for preterm birth or recurrent miscarriage. [53] [54]
Although progesterone does not have significant AR-mediated androgenic or antiandrogenic activity, it is a precursor and intermediate, albeit distant, in the biosynthesis of androgens from cholesterol. [55] [56] For this reason, there has been some speculation that exogenous progesterone could be transformed into androgens by certain tissues that express the requisite enzymes. [56] [57] Progesterone is converted by 17α-hydroxylase into 17α-hydroxyprogesterone; 17α-hydroxyprogesterone is converted by 17,20-lyase into androstenedione; and androstenedione is converted by 17β-hydroxysteroid dehydrogenases into testosterone. [55] CYP17A1, the cytochrome P450 gene that encodes 17α-hydroxylase and 17,20-lyase, is expressed mainly in the gonads (ovaries and testes) and the adrenal glands. [58] However, while it is theoretically possible that progesterone could be transformed in the body into androgens, no androgenic effects have been observed in animal studies. [45] In addition, clinical studies, in which women were treated with 100 to 300 mg/day oral progesterone, have found no or only a small increase in levels of 17α-hydroxyprogesterone, and no change in androgen levels, including of dehydroepiandrosterone, androstenedione, and testosterone. [50] [59] [46] In these studies, levels of estradiol and cortisol, which progesterone is also a precursor of, did not change either, although levels of 11-deoxycorticosterone increased significantly. [59] [46] Levels of androgens, like testosterone and dihydrotestosterone (DHT), also do not increase going from the follicular phase to the luteal phase of the menstrual cycle in premenopausal women (progesterone levels being high in the luteal phase). [60]
Progesterone is a substrate for 5α-reductase, and has been found to act as a competitive inhibitor of this enzyme in vitro in a variety of studies. [1] In one study, it showed IC50 values of 1,375 nM and 88 nM (in the presence of 50 nM androstenedione as the substrate) for 5α-reductase types 1 and 2, respectively. [61] 5α-Reductase is highly expressed in skin, hair follicles, and prostate gland, and is responsible for the transformation of testosterone into the several-fold more potent androgen DHT in such tissues. [62] [63] As such, it has been suggested that progesterone might possess some antiandrogenic effect via acting as a 5α-reductase inhibitor. [1] However, inhibition of 5α-reductase by progesterone is described as a weak effect that has only been demonstrated in vitro and at supraphysiological concentrations. [64] [65] In accordance, physiological levels of circulating progesterone have not been found to importantly influence circulating DHT concentrations. [60] [66]
Congenital 5α-reductase 2 deficiency is a rare intersex condition which is associated with ambiguous genitalia in male fetuses due to a deficiency in DHT production during genital differentiation. [63] Experimental prenatal exposure to established 5α-reductase inhibitors like finasteride has been found to produce similar feminized genital defects in male animals including rodents and monkeys. [67] In contrast, exogenous administration of progesterone to pregnant rodents and monkeys has resulted in minimal abnormality in either male or female pups. [68] [69] [70] [71] In addition, endogenous progesterone levels naturally increase to extremely high concentrations during pregnancy, yet genital defects do not occur. [72] In accordance, while total concentrations of progesterone in pregnant women at term are around 150 ng/mL (~500 nM), free or unbound and hence bioactive concentrations of progesterone are only about 3 ng/mL (~10 nM) due to the high plasma protein binding of progesterone, and these concentrations are still well below the aforementioned IC50 values for inhibition of 5α-reductase types 1 and 2. [73] [74] As with endogenous progesterone during pregnancy, exogenous supplemental progesterone during pregnancy has been found not to increase the risk of hypospadias in male infants. [75]
Although systemic progesterone does not appear to be an effective 5α-reductase inhibitor, topical progesterone may produce potent inhibition of 5α-reductase in the skin due to the very high local concentrations that occur. [76] [77] A study found that topical progesterone applied to the pubic area in men inhibited 5α-reductase in the skin in this region by 75%. [77] [78] In addition to inhibition of 5α-reductase, progesterone is metabolized by 5α-reductase into 5α-dihydroprogesterone (5α-DHP), a compound reported to have some antagonistic activity at the AR. [78] [79] However, this compound appears to have no systemic antiandrogenic activity. [80] In spite of its apparent 5α-reductase inhibition, the effectiveness of topical progesterone in the treatment of pattern hair loss has been poor. [79] [81] [82]
Certain progestins have been found to stimulate the proliferation of MCF-7 breast cancer cells in vitro , an action that is independent of the classical PRs and is instead mediated via the progesterone receptor membrane component-1 (PGRMC1). [83] Progesterone, nomegestrol acetate, and chlormadinone acetate act neutrally and do not stimulate proliferation, whereas norethisterone, desogestrel, levonorgestrel, and drospirenone strongly stimulate proliferation and medroxyprogesterone acetate, dienogest, and dydrogesterone weakly stimulate proliferation. [83] [84] As such, progesterone differs from some but not all progestins in the activity mediating this PGRMC1-dependent effect. [83] It is unclear if these findings may explain the different risks of breast cancer observed with progesterone, dydrogesterone, and other progestins such as medroxyprogesterone acetate and norethisterone in clinical studies. [85]
The PRs are expressed widely throughout the body, including in the uterus, cervix, vagina, fallopian tubes, breasts, fat, skin, pituitary gland, hypothalamus, and elsewhere throughout the brain. [1] [86] Through activation of the PRs (as well as the mPRs), progesterone has many effects, including the following: [1] [86]
Many of the effects of progesterone require estrogen, as estrogens prime tissues for progesterone by inducing expression of the PRs. [1] [86] The PRs are induced in the breasts by estrogens, and for this reason, it is assumed that progestogens cannot mediate breast changes in the absence of estrogens. [101]
Progesterone also lowers blood pressure and reduces water and salt retention among other effects via its antimineralocorticoid activity. [1] [39]
Progesterone can produce sedative, hypnotic, anxiolytic, euphoric, cognitive-, memory-, and motor-impairing, anticonvulsant, and even anesthetic effects via formation of sufficiently high concentrations of its neurosteroid metabolites and consequent GABAA receptor potentiation in the brain. [38] [102] [103] [104]
Under normal physiological circumstances, progesterone secreted by the corpus luteum during the luteal phase of the menstrual cycle produces endometrial transformation of the estrogen-primed uterus in preparation for implantation and pregnancy. [105] Normal progesterone production during the luteal phase is 25 mg/day on average with a range of 15 to 50 mg/day. [106] [71] Progesterone levels during the luteal phase range from 7 ng/mL to 22 ng/mL using liquid chromatography–tandem mass spectrometry (LC–MS/MS) per one source. [107] Sustained progesterone levels of more than 5 ng/mL, perhaps approximately 10 ng/mL, are required for full endometrial transformation. [87] [108] Progesterone levels of more than 10 ng/mL are rarely associated with luteal-phase defect on the basis of endometrial biopsy. [109]
Luteal-phase levels of progesterone are said to be produced by 25 mg/day progesterone in oil solution by intramuscular injection or by 100 mg/day progesterone by vaginal or rectal administration. [71] [110] Progesterone by intramuscular injection in oil solution has been found to produce endometrial transformation at a dose of 10 or 20 mg/day for 14 days (total dose per cycle of 200 mg), whereas a single intramuscular injection of 200 mg progesterone in microcrystalline aqueous suspension provides endometrial transformation after 10 to 14 days. [111] A study found full and equivalent endometrial transformation with subcutaneous injection of 25 mg/day versus 50 mg/day progesterone in aqueous solution. [112] Due to a uterine first-pass effect and markedly higher uterine progesterone levels than with other routes, 45 mg/day vaginal progesterone, a dosage that achieves circulating progesterone levels of only 1 to 5 ng/mL, provides complete endometrial transformation. [113] [110] Conversely, intranasal administration of progesterone achieving progesterone levels of 2 to 5 ng/mL was ineffective. [113] Transdermal progesterone achieves very low progesterone levels and is considered to be ineffective for endometrial protection. [113] [114] [115]
The endometrial transformation dosage of oral micronized progesterone in women has been listed as 200 to 300 mg/day or 4,200 mg total per cycle. [116] [1] However, a clinical study found that 300 mg/day oral micronized progesterone was insufficient for full endometrial transformation. [117] Similarly, 600 to 1,000 mg/day oral micronized progesterone has been reported to be ineffective for achieving complete endometrial transformation. [113] [112] Despite inadequate endometrial transformation with oral progesterone, continuous 100 mg/day oral micronized progesterone or cyclic 200 mg/day oral micronized progesterone is effective for protection of the endometrium against estrogen-induced endometrial hyperplasia. [118] On the other hand, and in contrast to progestins, typical clinical doses of oral micronized progesterone have been associated with failure to prevent increased endometrial cancer risk caused by estrogen therapy. [119]
Progesterone, like all progestogens, has antiestrogenic effects in certain tissues such as the uterus, cervix, vagina, and breasts, and possibly also the brain. [1] [120] [121] These effects are mediated by activation of the PR in these tissues. [1] Progesterone does not have antiestrogenic effects in the more conventional sense of binding to and antagonizing the ER or binding to and inhibiting enzymes involved in estrogen biosynthesis. [1] Instead, for instance in the endometrium, progesterone causes downregulation of the ER and upregulation of the estrogen-inactivating enzymes 17β-hydroxysteroid dehydrogenase 2 (converts estradiol into estrone) and estrone sulfotransferase (converts estrone into estrone sulfate). [1] The antiestrogenic effects of progesterone and other progestogens form the basis for their only approved indication in menopausal hormone therapy: prevention of long-term unopposed estrogen-induced endometrial hyperplasia and increased endometrial cancer risk in women with intact uteruses. [1]
In the breasts, progesterone and other progestogens downregulate the ER as well as the estrogen-activating enzymes steroid sulfatase (converts estrone sulfate into estrone) and 17β-hydroxysteroid-dehydrogenase 1 (converts estrone into estradiol) and upregulates estrone sulfotransferase. [120] [121] However, other studies suggest that progestogens do not downregulate ER expression in the breasts. [122] [123] When applied directly to the breasts in women, progesterone can block the proliferative effects of estradiol. [124] [101] [125] [126] [127] [128] [129] [85] However, the concentrations were supraphysiological and the same may not be the case with more physiological concentrations. [127] [85] Cellular proliferation in the breasts is greatest in the luteal phase of the menstrual cycle, when progesterone levels are highest. [85]
It has been hypothesized that progestogens may counteract various effects of estrogens in the brain such as stimulatory and excitatory effects on neuronal activity. [1] Progesterone moreover has a special position among progestogens concerning such actions due to its inhibitory neurosteroid metabolites and their central depressant effects. [1] It has been suggested that these actions of progestogens may explain unfavorable effects on mood that have been reported with these medications in some women. [1] However, the mutual interactions of estrogens and progestogens in the brain in general are controversial and require more research. [1]
Progesterone can produce body-wide antiestrogenic effects at very high doses in both women and men via its antigonadotropic effects and consequent suppression of gonadal estrogen production (see below). [1] [130] These antigonadotropic effects are mediated by hyperactivation of the PR. [1] [130]
Progestogens have antigonadotropic effects at sufficiently high doses via activation of the PR and consequent negative feedback on and hence suppression of the hypothalamic–pituitary–gonadal axis (HPG axis). [130] This results in suppression of gonadotropin secretion and by extension interference with fertility and gonadal sex hormone production. [130] Progesterone prevents ovulation by suppressing the mid-cycle surge in gonadotropin secretion during the menstrual cycle. [131] [94]
The ovulation-inhibiting (i.e., contraceptive) dosage of oral crystalline (non-micronized) progesterone in women is 300 mg/day or greater. [71] [132] [1] [133] [134] However, this figure is based on limited clinical data. [71] In the clinical research in the 1950s that determined this dosage, ovulation inhibition occurred in 50 to 100% of women when assessed via measures including urinary pregnanediol excretion, daily basal body temperatures, endometrial biopsies, and vaginal smears. [132] [135] [136] [137] [138] Another study found that ovulation inhibition with 300 mg/day oral non-micronized progesterone occurred in a "proportion of the cases" when assessed via laparotomy. [137] A third study found that ovulation was inhibited in only 38% of women treated with 1,000 mg/day oral non-micronized progesterone. [133] A fourth publication stated that even 750 to 1,000 mg/day oral non-micronized progesterone had weak effects as evidenced by poor thermogenic effect, weak endometrial effect, and lack of production of withdrawal bleeding in amenorrheic women. [139] [140] Neumann and colleagues listed the ovulation-inhibiting dosage of oral non-micronized progesterone in women as 300 to 500 mg/day or as 400 mg/day but provided no other details. [134] [141] [142] [143]
In a study of a progesterone vaginal ring alone or in combination with estradiol that released 1.5 to 3 mg/day progesterone and achieved mean progesterone levels varying between 0.7 and 1.6 ng/mL (mean 0.9 ng/mL) during anovulatory cycles, ovulation occurred in 18 of 30 (60%) menstrual cycles. [144] A study of a vaginal progesterone ring that released almost 10 mg/day progesterone and maintained mean progesterone levels of 4.4 ng/mL (range 2.4–6.5 ng/mL) found that ovulation was inhibited in some but not all women. [145] [146] In another study, a progesterone vaginal ring that released about 10 mg/day progesterone and produced progesterone levels of around 4 ng/mL (range 3–5.2 ng/mL) resulted in ovulation occurring in 25% of treated breastfeeding women compared to a rate of 56% in a control group of breastfeeding women. [147] A study in rhesus monkeys found that a vaginal ring delivering 0.235 or 1.77 mg/day progesterone inhibited ovulation in all monkeys at the higher dose and in a proportion of monkeys at the lower dose. [68] [148] A dose of progesterone of 5 to 10 mg/day by intramuscular injection has been found to prevent ovulation in women and has been considered effective as a progestogen-only injectable contraceptive. [149] [150] [151]
Short-term therapy with 300 mg/day oral progesterone had no effect on luteinizing hormone pulse frequency in women. [152] Treatment with a high dosage of oral progesterone of 100 mg four times per day (or 400 mg/day total) in men for 10 days did not cause any change in testosterone levels, suggesting that oral progesterone has little or no antigonadotropic effect in males at typical clinical dosages. [38] [153] In addition, a study found that administration of 1,000 mg/day oral progesterone for 3 months had no significant effect on urinary gonadotropin excretion. [71] On the other hand, a single 50 mg intramuscular injection of progesterone, which is associated with high progesterone levels of approximately 50 ng/mL (or early- to mid-pregnancy levels), [154] [155] [156] resulted in substantial (50–60%) suppression of luteinizing hormone, follicle-stimulating hormone, and testosterone levels in men. [157] [158] Similarly, continuous or intermittent intravenous injections of 100 to 400 mg/day progesterone for 10 days significantly decreased urinary gonadotropin excretion. [71] [159] Progestogens in general are able to suppress gonadal testosterone production in men by a maximum of about 70 to 80% or to just above castrate levels when used at sufficiently high doses. [160] [161]
A study using 50 mg/day progesterone by intramuscular injection in five men found that the medication produced azoospermia or severe oligozoospermia in all within 10 weeks, suppressed libido, erectile function, and ejaculate volume to minimal levels, produced slight gynecomastia in two of the men, moderately decreased testicular size, and impaired testicular morphology. [149] [162] [163] [158] [164] [165] [166] Upon discontinuation, sperm counts returned to normal in the men within 14 to 17 weeks. [149] [162] [158] [164] [166] In another study, 100 mg rectal suppositories of progesterone given five times per day for 9 days resulted in progesterone levels of 5.5 to 29 ng/mL and suppressed circulating testosterone and growth hormone levels by about 50% in men, but did not affect libido or erectile potency with this short duration of therapy. [149] [167]
Progesterone can have progonadotropic effects under certain circumstances. [131]
Progesterone, through the actions of neurosteroid active metabolites such as allopregnanolone and pregnanolone, is a potent positive allosteric modulator of the GABAA receptor, the major signaling receptor of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). [15] It can produce sedative, hypnotic, anxiolytic, euphoric, cognitive-, memory-, and motor-impairing, anticonvulsant, and even anesthetic effects with formation of sufficiently high concentrations of its neurosteroid metabolites and consequent GABAA receptor potentiation in the brain. [38] [102] [103] [104] These actions and effects are characteristically similar to those of other GABAA receptor positive allosteric modulators like alcohol, barbiturates, and benzodiazepines. [104]
Similarly to other GABAA receptor positive allosteric modulators like alcohol, barbiturates, and benzodiazepines, tolerance has been found to develop with exposure to increased levels of allopregnanolone and related inhibitory neurosteroids. [168] [169] This includes downregulation and desensitization of the GABAA receptor, reduced effects of allopregnanolone and other GABAA receptor activators (e.g., GABA and benzodiazepines), and rebound or withdrawal effects upon falls in allopregnanolone levels. [168] [169] In addition, changes in allopregnanolone levels have been implicated in adverse neuropsychiatric effects associated with the menstrual cycle (e.g., dysphoria, depression, anxiety, irritability) and postpartum period (e.g., postpartum depression), as well as in catamenial epilepsy (seizures). [170] [171] Low and high levels of allopregnanolone seem to have a neutral effect on mood, whereas moderate levels have a negative effect, which may underlie the symptoms of premenstrual syndrome and premenstrual dysphoric disorder that are observed in 30 to 40% of premenopausal women. [170] [171] [172] This U-shaped effect on mood appears to be a common property of GABAA receptor positive allosteric modulators. [170] [171]
A progestogen, also referred to as a progestagen, gestagen, or gestogen, is a type of medication which produces effects similar to those of the natural female sex hormone progesterone in the body. A progestin is a synthetic progestogen. Progestogens are used most commonly in hormonal birth control and menopausal hormone therapy. They can also be used in the treatment of gynecological conditions, to support fertility and pregnancy, to lower sex hormone levels for various purposes, and for other indications. Progestogens are used alone or in combination with estrogens. They are available in a wide variety of formulations and for use by many different routes of administration. Examples of progestogens include natural or bioidentical progesterone as well as progestins such as medroxyprogesterone acetate and norethisterone.
Desogestrel is a progestin medication which is used in birth control pills for women. It is also used in the treatment of menopausal symptoms in women. The medication is available and used alone or in combination with an estrogen. It is taken by mouth.
Drospirenone is a progestin and antiandrogen medication which is used in birth control pills to prevent pregnancy and in menopausal hormone therapy, among other uses. It is available both alone under the brand name Slynd and in combination with an estrogen under the brand name Yasmin among others. The medication is an analog of the drug spironolactone. Drospirenone is taken by mouth.
Norethisterone acetate (NETA), also known as norethindrone acetate and sold under the brand name Primolut-Nor among others, is a progestin medication which is used in birth control pills, menopausal hormone therapy, and for the treatment of gynecological disorders. The medication available in low-dose and high-dose formulations and is used alone or in combination with an estrogen. It is ingested orally.
Tibolone, sold under the brand name Livial among others, is a medication which is used in menopausal hormone therapy and in the treatment of postmenopausal osteoporosis and endometriosis. The medication is available alone and is not formulated or used in combination with other medications. It is taken by mouth.
Norethisterone, also known as norethindrone and sold under many brand names, is a progestin medication used in birth control pills, menopausal hormone therapy, and for the treatment of gynecological disorders. The medication is available in both low-dose and high-dose formulations and both alone and in combination with an estrogen. It is used by mouth or, as norethisterone enanthate, by injection into muscle.
Gestodene, sold under the brand names Femodene and Minulet among others, is a progestin medication which is used in birth control pills for women. It is also used in menopausal hormone therapy. The medication is available almost exclusively in combination with an estrogen. It is taken by mouth.
Dydrogesterone, sold under the brand name Dydroboon & Duphaston among others, is a progestin medication which is used for a variety of indications, including threatened or recurrent miscarriage during pregnancy, dysfunctional bleeding, infertility due to luteal insufficiency, dysmenorrhea, endometriosis, secondary amenorrhea, irregular cycles, premenstrual syndrome, and as a component of menopausal hormone therapy. It is taken by mouth.
Ethisterone, also known as ethinyltestosterone, pregneninolone, and anhydrohydroxyprogesterone and formerly sold under the brand names Proluton C and Pranone among others, is a progestin medication which was used in the treatment of gynecological disorders but is now no longer available. It was used alone and was not formulated in combination with an estrogen. The medication is taken by mouth.
Dienogest, sold under the brand name Visanne among others, is a progestin medication which is used in birth control pills and in the treatment of endometriosis. It is also used in menopausal hormone therapy and to treat heavy periods. Dienogest is available both alone and in combination with estrogens. It is taken by mouth.
Medrogestone, sold under the brand name Colprone among others, is a progestin medication which has been used in menopausal hormone therapy and in the treatment of gynecological disorders. It is available both alone and in combination with an estrogen. It is taken by mouth.
Promegestone, sold under the brand name Surgestone, is a progestin medication which is used in menopausal hormone therapy and in the treatment of gynecological disorders. It is taken by mouth.
Normethandrone, also known as methylestrenolone or methylnortestosterone and sold under the brand name Metalutin among others, is a progestin and androgen/anabolic steroid (AAS) medication which is used in combination with an estrogen in the treatment of amenorrhea and menopausal symptoms in women. It is taken by mouth.
Demegestone, sold under the brand name Lutionex, is a progestin medication which was previously used to treat luteal insufficiency but is now no longer marketed. It is taken by mouth.
Trimegestone, sold under the brand names Ondeva and Totelle among others, is a progestin medication which is used in menopausal hormone therapy and in the prevention of postmenopausal osteoporosis. It was also under development for use in birth control pills to prevent pregnancy, but ultimately was not marketed for this purpose. The medication is available alone or in combination with an estrogen. It is taken by mouth.
Nomegestrol acetate (NOMAC), sold under the brand names Lutenyl and Zoely among others, is a progestin medication which is used in birth control pills, menopausal hormone therapy, and for the treatment of gynecological disorders. It is available both alone and in combination with an estrogen. NOMAC is taken by mouth. A birth control implant for placement under the skin was also developed but ultimately was not marketed.
Trengestone, sold under the brand names Reteroid, Retroid, and Retrone, is a progestin medication which was formerly used to treat menstrual disorders but is now no longer marketed. It is taken by mouth.
20α-Dihydroprogesterone (20α-DHP), also known as 20α-hydroxyprogesterone (20α-OHP), is a naturally occurring, endogenous progestogen. It is a metabolite of progesterone, formed by the 20α-hydroxysteroid dehydrogenases (20α-HSDs) AKR1C1, AKR1C2, and AKR1C3 and the 17β-hydroxysteroid dehydrogenase (17β-HSD) HSD17B1. 20α-DHP can be transformed back into progesterone by 20α-HSDs and by the 17β-HSD HSD17B2. HSD17B2 is expressed in the human endometrium and cervix among other tissues. In animal studies, 20α-DHP has been found to be selectively taken up into and retained in target tissues such as the uterus, brain, and skeletal muscle.
Progesterone (P4) is a medication and naturally occurring steroid hormone. It is a progestogen and is used in combination with estrogens mainly in hormone therapy for menopausal symptoms and low sex hormone levels in women. It is also used in women to support pregnancy and fertility and to treat gynecological disorders. Progesterone can be taken by mouth, vaginally, and by injection into muscle or fat, among other routes. A progesterone vaginal ring and progesterone intrauterine device used for birth control also exist in some areas of the world.
The pharmacokinetics of progesterone, concerns the pharmacodynamics, pharmacokinetics, and various routes of administration of progesterone.
17α-Hydroxyprogesterone caproate is a depot progestogen which is entirely free of side actions. The dose required to induce secretory changes in primed endometrium is about 250 mg. per menstrual cycle.
The results showed that after injection the concentration of plasma MA increased rapidly. The meantime of peak plasma MA level was 3rd day, there was a linear relationship between log of plasma MA concentration and time (day) after administration in all subjects, elimination phase half-life t1/2β = 14.35 ± 9.1 days.
Drospirenone and progesterone exhibited low binding affinities to the rat GR as is documented by 1% and 11% RBA values compared to the reference dexamethasone, respectively. Similar results were reported elsewhere.8 In accordance with the low affinity to the GR, progesterone and drospirenone showed weak or no detectable agonistic activities, respectively, in the GR-dependent transactivation assay (Figure 2A and Figure 2B). Furthermore, both progestins were devoid of antiglucocorticoid activity in vitro. These data are in agreement with in vivo studies carried out with rats where drospirenone and progesterone showed neither glucocorticoid nor antiglucocorticoid activity.8
Natural progesterone is devoid of any androgenic activity that might compromise lipoprotein metabolism or induce teratogenicity.
It has been observed that micronized progesterone has no suppressive effects on high-density lipoprotein-cholesterol (HDL-C). Jensen et al have proved that oral micronized progesterone has no adverse effect on serum lipids. These preparations have the same antiestrogenic and antimineralocorticoid effect but no androgenic action. It does not affect aldosterone synthesis, blood pressure, carbohydrate metabolism or mood changes. No side effects have been reported as far as lipid profile, coagulation factors and blood pressure are concerned.
Natural progesterone is devoid of any androgenic activity and is thus extensively used in assisted reproduction, sometimes for long periods of time.
Progestogens differ in their relative metabolic and androgenic effects; for example MPA is minimally androgenic, but does counteract the rise in HDL-cholesterol caused by oestrogen therapy. In contrast, oral micronized progesterone does not mitigate against increased HDL-cholesterol levels.
The mean values of TT, FT, SHBG, DHEAS, A4, and 17-OHP did not change with OMP administration. However, a higher 17-OHP level was observable at the completion of OMP administration (week 2).
Natural progesterone, such as micronized progesterone, has no androgenic properties, whereas some synthetic progestins, such as MPA and norethisterone acetate, possess androgenic side effects, which raise the concern of potentially harmful effects on blood pressure.
The chemical structure of progesterone and testosterone are remarkably similar; they differ only in the side chain at the 17-carbon position. The possibility that progesterone can be transformed to testosterone has been considered good by many. If true, it could then be a source of androgens in women. [...] Laboratory evidence exists that progesterone can be converted to testosterone in vitro by human and animal ovarian and testicular tissue.44-47 Although the role of progesterone in acne and its effect on sebaceous gland activity is not fully established, the possibility that endogenous progesterone is a precursor of testosterone or of another androgenic substance invites further exploration.48,49
The only concern Voigt and Hsia expressed about the use of progesterone as an anti-androgen was the possibility that the small amount of hormone which reached the circulation could be converted into testosterone by the sexual organs, mainly the testes.
Plasma concentrations of oestradiol were unchanged by giving progesterone.
These studies suggest that [...] a rise in serum progesterone has only a minimal effect on circulating levels of the active 5α‐reduced androgen metabolites. [...] Progesterone has been shown to be a potent in vitro inhibitor of cutaneous 5α-reductase (Mauvais-Jarvis et al., 1974). However we found only a small reduction in serum DHT levels in the late luteal phase in ovulatory women and no change in serum 3α-diol. Hence the rise in serum progesterone in ovulatory women has only a minimal effect on the circulating levels of the major active 5α-reduced androgens in vivo.
Progesterone has been shown to inhibit 5α-reductase, another important enzyme in steroid hormone metabolism, (Dean and Winter, 1984; Beckmann et al., 1993; Cassidenti et al., 1991; Kadohama et al., 1983; Mauvais-Jarvis et al., 1974; Dube et al., 1975). However, this is a weak effect that has only been demonstrated at supra-physiological concentrations and in vitro conditions.
Progesterone (and other progestational agents) inhibit testosterone from expressing its activity at the target sites (Kincl, 1971a). Mice and rats are the test animals of choice (Dorfman, 1963a,b). Inhibition of 5α-reductase activity of binding to cytosol and nuclear receptors has been shown to be the steps at which antiandrogens express their activity (Neumann and Steinbeck, 1974). Relatively high amounts are needed to achieve a significant effect (Table 2.16).
Early studies on its use as an oral contraceptive showed that, at 300 mg/day (5th to 25th day of the menstrual cycle), progesterone was effective in preventing ovulation through four cycles (263). The related effect of larger doses of progesterone on gonadotropin excretion also has been investigated. Rothchild (264) found that continuous or intermittent intravenously administered progesterone (100-400 mg/day) for 10 days depressed the total amount of gonadotropin excreted into the urine. However, Paulsen et al. (265) found that oral progesterone at 1000 mg/day for 87 days did not have a significant effect on urinary gonadotropin excretion. The efficacy of progesterone as an oral contraceptive was never fully tested, because synthetic progestational agents, which were orally effective, were available.
Throughout the reproductive years, some women note swelling of the breast around the latter part of each menstrual cycle before the onset of menstruation. The water retention and subsequent swelling of breast tissue during this phase of the menstrual cycle are thought to be due to high levels of circulating progesterone stimulating the secretory cells of the breast.12
When administered before the estrogen stimulus, or in high doses (achieving a blood level greater than 2 ng/mL), progesterone blocks the midcycle LH surge.
In the presence of circulating levels of approximately 4 μg/L or greater of progesterone, most women experience a 0.5° to 1°F rise in basal body temperature.
It seems that [progesterone] levels of approximately 10 ng/mL are sufficient to sustain morphological and functional endometrial development. [...] Oral micronized P (100 mg three times) was investigated in ovarian failure patients in 12 cycles after adequate E2 priming (84). The serum P levels achieved were subphysiologic and incapable of inducing a normal secretory response in the endometrium.
Table 1 Publications on ovulation inhibition doses of progestins: Progestin: Progesterone. Reference: Pincus (1956). Method: Urinary pregnanediol. Daily dose (mg): 300.000. Total number of cycles in all subjects: 61. Total number of ovulation in all subjects: 30. % of ovulation in all subjects: 49.
The results of testing the effects of progesterone on ovulation in 13 patients at the Margaret Sanger Research Bureau are presented. The patients had normal menstrual cycles and showed clear evidence of ovulation. Each patient was given 1000 [mg] of [oral] progesterone daily during the midperiod for 10 or 12 days during 16 cycles. Ovulation was inhibited in 6 cycles. No disturbance in menstrual rhythm was observed. 3 of 12 patients with longstanding infertility histories became pregnant within 2-4 months after the cessation of progesterone therapy.
Table 1: Effects of oral progesterone on three indexes of ovulation: Medication: Progesterone. Number: 69. Mean cycle length: 25.5 ± 0.59. Per cent positive for ovulation by: Basal temperature: 27. Endometrial biopsy: 18. Vaginal smear: 6. [...] we settled on 300 mg. per day [oral progersterone] as a significantly effective [ovulation inhibition] dosage, and this was administered from the fifth day through the twenty-fourth day of the menstrual cycle. [...] We observed each of 33 volunteer subjects during a control, nontreatment cycle and for one to three successive cycles of medication immediately following the control cycle. As indexes of the occurrence of ovulation, daily basal temperatures and vaginal smears were taken, and at the nineteenth to twenty-second day of the cycle an endometrial biopsy. [...] Although we thus demonstrated the ovulation-inhibiting activity of progesterone in normally ovulating women, oral progesterone medication had two disadvantages: ( l) the large daily dosage ( 300 mg.) which presumably would have to be even larger if one sought 100 per cent inhibition1 [...]
Ishikawa et al. (1957) employing the same regime of progesterone administration also observed suppression of ovulation in a proportion of the cases taken to laparotomy. Although sexual intercourse was practised freely by the subjects of our experiments and those of Ishikawa el al., no pregnancies OCcurred. Since ovulation presumably took place in a proportion of cycles, the lack of any pregnancies may be due to chance, but Ishikawa et al. (1957) have presented data indicating that in women receiving oral progesterone the cervical mucus becomes impenetrable to sperm.
Daily intramuscular injection of 5 to 10 mg of progesterone from days 7 to 23 suppresses LH and FSH and prevents ovulation (569). Progestogens also lead to a reduction in gonadotropin levels.