Kallmann syndrome

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Kallmann syndrome
Other namesKallmann's hereditary anosmia
Specialty Endocrinology
Symptoms Absent or delayed puberty, infertility, inability to smell
Complications Osteoporosis
Usual onset Present at birth
DurationLifelong
Treatment Hormone replacement therapy
Gonadotropin therapy
Frequency1:30,000 (males), 1:125,000 (females)

Kallmann syndrome (KS) is a genetic disorder that prevents a person from starting or fully completing puberty. Kallmann syndrome is a form of a group of conditions termed hypogonadotropic hypogonadism. To distinguish it from other forms of hypogonadotropic hypogonadism, Kallmann syndrome has the additional symptom of a total lack of sense of smell (anosmia) or a reduced sense of smell. [1] [2] [3] If left untreated, people will have poorly defined secondary sexual characteristics, show signs of hypogonadism, almost invariably are infertile and are at increased risk of developing osteoporosis. [1] A range of other physical symptoms affecting the face, hands and skeletal system can also occur. [2]

Contents

The underlying cause is a failure in the correct production or activity of gonadotropin-releasing hormone by the hypothalamus. This results in low levels of the sex hormones testosterone in males or oestrogen and progesterone in females. Diagnosis normally occurs during teenage years when puberty fails to start. [3]

Lifelong treatment for both sexes is normally required. Hormone replacement therapy (HRT) is the major form of treatment with the aim to replace the missing testosterone or oestrogen and progesterone. Specialised fertility treatments are also available. [4]

The condition is more commonly diagnosed in males than in females. [5] A 2011 study of the Finnish population produced an estimated incidence of 1 in 48,000 people overall, with 1 in 30,000 for males and 1 in 125,000 for females. [6] Kallmann syndrome was first described by name in a paper published in 1944 by Franz Josef Kallmann, a German-American geneticist. [7] [8] The link between anosmia and hypogonadism had already been noted by Spanish doctor Aureliano Maestre de San Juan in 1856. [9] [10]

Signs and symptoms

19 year old with Kallmann syndrome before diagnosis and treatment 19 year old Kallmann syndrome patient, pre-diagnosis.jpg
19 year old with Kallmann syndrome before diagnosis and treatment
Singer Jimmy Scott (r), whose unusual voice was due to Kallman syndrome Jimmy Scott.jpg
Singer Jimmy Scott (r), whose unusual voice was due to Kallman syndrome

It is normally difficult to distinguish a case of Kallmann syndrome (KS)/hypogonadotropic hypogonadism (HH) from a straightforward constitutional delay of puberty. However, if puberty has not started by either age 14 (girls) or 15 (boys) years and one or more of the non-reproductive features mentioned below is present, then a referral to reproductive endocrinologist might be advisable. [11] [1] [5]

The features of KS and other forms of HH can be split into two different categories; "reproductive" and "non-reproductive". [3] [10] [4] [12] [2]

Reproductive features

Non-reproductive features

The exact genetic nature of each particular case of KS/HH will determine which, if any, of the non-reproductive features will occur. The severity of the symptoms will also vary from case to case. Even family members will not show the same range or severity of symptoms. [2] [5]

KS/HH is most often present from birth but adult onset versions are found in both males and females. The hypothalamic-pituitary-gonadal axis (HPG axis) functions normally at birth and well into adult life, giving normal puberty and normal reproductive function. The HPG axis then either fails totally or is reduced to a very low level of GnRH release in adult life with no obvious cause (e.g. a pituitary tumour). This will lead to a fall in testosterone or oestrogen levels and infertility. [13] [16]

Functional hypothalamic amenorrhoea is seen in females where the HPG axis is suppressed in response to physical or psychological stress or malnutrition but is reversible with the removal of the stressor. [1]

Some cases of KS/HH appear to reverse during adult life where the HPG axis resumes its normal function and GnRH, LH, and FSH levels return to normal levels. This occurs in an estimated 10 to 22% of people, primarily normosmic CHH cases rather than KS cases and only found in people who have undergone some form of testosterone replacement therapy. It is only normally discovered when testicular volume increases while on testosterone treatment alone and testosterone levels return to normal when treatment is stopped. This type of KS/HH rarely occurs in cases where males have had a history of un-descended testes. [5] [3]

Affected individuals with KS and other forms of HH are almost invariably born with normal sexual differentiation; i.e., they are physically male or female. This is due to the human chorionic gonadotrophin (hCG) produced by placenta at approximately 12 to 20 weeks gestation (pregnancy) which is normally unaffected by having KS or CHH. [17]

People with KS/HH lack the surge of GnRH, LH, and FSH that normally occurs between birth and six months of age. This surge is particularly important in infant boys as it helps with testicular descent into the scrotum. The surge of GnRH/LH/FSH in non KS/HH children gives detectable levels of testosterone in boys and oestrogen and progesterone in girls. The lack of this surge can sometimes be used as a diagnostic tool if KS/HH is suspected in a newborn boy, but is not normally distinct enough for diagnosis in girls. [3]

Osteoporosis

One possible side effect of having KS/CHH is the increased risk of developing secondary osteoporosis or osteopenia. Oestrogen (females) or testosterone (males) is essential for maintaining bone density. [18] Deficiency in either testosterone or oestrogen can increase the rate of bone resorption while at the same time slowing down the rate of bone formation. Overall this can lead to weakened, fragile bones which have a higher tendency to fracture.[ citation needed ]

Even a short time with low oestrogen or testosterone, as in cases of delayed diagnosis of KS/CHH can lead to an increased risk of developing osteoporosis but other risk factors, such as smoking are involved so the risk of developing it will vary from person to person. Bone density scans are recommended to monitor the bone mineral density. [13]

The bone density scan is known as a dual energy X-ray absorptiometry scan (DEXA or DXA scan). It is a simple test, taking less than 15 minutes to perform. It involves taking a specialised X-ray picture of the spine and hips and measuring the bone mineral density and comparing the result to the average value for a young healthy adult in the general population. [19]

Adequate calcium levels and, probably, more importantly, vitamin D levels are essential for healthy bone density. Some people with KS/CHH will have their levels checked and may be prescribed extra vitamin D tablets or injections to try to prevent the condition getting worse. The role of vitamin D for general overall health is under close scrutiny at the moment with some researchers claiming vitamin D deficiency is prevalent in many populations and can be linked to other diseases. [20]

Some people with severe osteoporosis might be prescribed bisphosphonates to preserve bone mass, in addition to hormone replacement therapy. [21]

Genetics

The genetic and molecular basis of idiopathic hypogonadotropic hypogonadism The genetic and molecular basis of idiopathic hypogonadotropic hypogonadism.jpg
The genetic and molecular basis of idiopathic hypogonadotropic hypogonadism

To date at least 25 different genes have been implicated in causing Kallmann syndrome or other forms of hypogonadotropic hypogonadism through a disruption in the production or activity of GnRH (37). These genes involved cover all forms of inheritance and no one gene defect has been shown to be common to all cases which makes genetic testing and inheritance prediction difficult. [22] [23]

The number of genes known to cause cases of KS/CHH is still increasing. [12] In addition it is thought that some cases of KS/CHH are caused by two separate gene defects occurring at the same time. [5]

Individual gene defects can be associated with specific symptoms which can help in identifying which genes to test for. [5] [2] Between 35 and 45% of cases of KS/CHH have an unknown genetic cause. [24]

The ANOS1 gene defect (previously known as KAL-1) was the first one discovered and the one most commonly tested for. It causes the x-linked form of Kallmann syndrome and is associated with the additional symptoms of anosmia, bimanual synkinesis and renal agenesis. This defect is thought to be responsible for between 5 and 10% of all Kallmann syndrome/CHH cases. [5] [2]

Pathophysiology

Shows the normal hormonal control of puberty from the hypothalamus down to the testes or ovaries and their negative feedback mechanisms. The negative feedback control allows just the right amount of hormone to be released according to the needs of the body at that time. Flow diagram showing normal hormonal control of puberty.gif
Shows the normal hormonal control of puberty from the hypothalamus down to the testes or ovaries and their negative feedback mechanisms. The negative feedback control allows just the right amount of hormone to be released according to the needs of the body at that time.
Shows the effect of the interruption of GnRH hormone release from the hypothalamus and the subsequent inability of the testes and ovaries to function correctly at puberty as seen in cases of KS/HH. In most cases of KS/HH the testes and ovaries are able to function correctly, but fail to do so because they have not had the correct hormonal signals. Diagram showing the disruption of the hormonal pathways of puberty due to the failure of GnRH release seen in KS and HH.gif
Shows the effect of the interruption of GnRH hormone release from the hypothalamus and the subsequent inability of the testes and ovaries to function correctly at puberty as seen in cases of KS/HH. In most cases of KS/HH the testes and ovaries are able to function correctly, but fail to do so because they have not had the correct hormonal signals.
The structure of GNRH1 (from PDB: 1YY1 ) GNRH1 structure.png
The structure of GNRH1
(from PDB: 1YY1 ​)

The underlying cause of Kallmann syndrome or other forms of hypogonadotropic hypogonadism is a failure in the correct action of the hypothalamic hormone GnRH. The term isolated GnRH deficiency (IGD) has increasingly been used to describe this group of conditions as it highlights the primary cause of these conditions and distinguishes them from other conditions such as Klinefelter syndrome or Turner syndrome which share some similar symptoms but have a different etiology. [25] The term hypogonadism describes a low level of circulating sex hormones; testosterone in males and oestrogen and progesterone in females. Hypogonadism can occur through a number of different mechanisms. The use of the term hypogonadotropic relates to the fact that the hypogonadism found in HH is caused by a disruption in the production of the gonadotropin hormones normally released by the anterior pituitary gland known as luteinising hormone (LH) and follicle stimulating hormone (FSH). [12] [24] Failure in GnRH activity can otherwise be due to the absence of the GnRH releasing neurons inside the hypothalamus. HH can occur as an isolated condition with just the LH and FSH production being affected or it can occur in combined pituitary deficiency conditions.[ citation needed ]

In the first 10 weeks of normal embryonic development, the GnRH releasing neurons migrate from their original source in the nasal region and end up inside the hypothalamus. These neurons originate in an area of the developing head, the olfactory placode, that will give rise to the olfactory epithelium; they then pass through the cribriform plate, along with the fibres of the olfactory nerves, and into the rostral forebrain. From there they migrate to what will become the hypothalamus. Any problems with the development of the olfactory nerve fibres will prevent the progression of the GnRH releasing neurons towards the brain. [26]

Diagnosis

Diagnosing KS and other forms of CHH is complicated by the difficulties in distinguishing between a normal constitutional delay of puberty or a case of KS/CHH. [27] [4] [28] The diagnosis is often one of exclusion found during the workup of delayed puberty. [29] [30] [31]

In males, the use of age appropriate levels of testosterone can help to distinguish between a case of KS/CHH from a case of delayed puberty. If no puberty is apparent, especially no testicular development, then a review by a reproductive endocrinologist may be appropriate. If puberty is not apparent by the age of 16 then the person should be referred for endocrinological review. [32] Post natal diagnosis of KS/CHH before the age of 6 months is sometimes possible as the normal post natal hormonal surge of gonadotropins along with testosterone or oestrogen is absent in babies with KS/CHH. This lack of detectable hormones in the blood can be used as a diagnostic indicator, especially in male infants. [33]

In females, diagnosis is sometimes further delayed as other causes of amenorrhoea normally have to be investigated first before a case of KS/CHH is considered. [34]

Tanner scale-female Tanner scale-female.svg
Tanner scale-female

Diagnosis of KS/CHH normal involves a range of clinical, biochemical and radiological tests to exclude other conditions that can cause similar symptoms.[ citation needed ]

Clinical tests

[3] [2]

Lab tests

[3] [2]

Medical imaging

[3] [2]

Treatment

Testosterone gel sachets, Testosterone undecanoate injection (Nebido), Human chorionic gonadotropin (hCG) injection, Menotropin injection (hMG). Kallmann treatment methods.jpg
Testosterone gel sachets, Testosterone undecanoate injection (Nebido), Human chorionic gonadotropin (hCG) injection, Menotropin injection (hMG).

For both males and females, the initial aim for treatment is the development of the secondary sexual characteristics normally seen at puberty. [2] [35] [30] [31] [36] Once this has been achieved, continued hormone replacement therapy is required for both males and females to maintain sexual function, bone health, libido and general wellbeing. [3] In males, testosterone replacement therapy is required for the maintenance of normal muscle mass. [2]

Early treatment is sometimes required for male infants with suspected KS/CHH to correct undescended testes and micropenis if present with the use or surgery or gonadotropin or DHT treatment. Females with KS/CHH normally do not require any treatment before adolescence. Currently, no treatments exist for the lack of sense of smell, mirror movement of the hands or the absence of one kidney. [3]

Treatment for both males and females with KS/CHH normally consists of one of three options which can be used for both hormone replacement therapy and/or fertility treatment. [2] [3]

Hormone replacement therapy

The method and dose of treatment will vary depending on the individual being treated. Initial treatment is normally made with lower doses in younger patients in order to develop the secondary sexual characteristics before adult doses are reached. [2]

For males with KS/CHH the types of testosterone delivery include daily patches, daily gel use, daily capsules, subcutaneous or intramuscular injections or six-monthly implants. Different formulations of testosterone are used to ensure both the anabolic and androgenic effects of testosterone are achieved. [3] [4] Nasal testosterone delivery methods have been developed but their use in KS/CHH treatment has not been formally evaluated. [2]

Gonadotropin therapy, in the form of human chorionic gonadotropin (hCG) injections, with or without the use of FSH, can also be used in male patients to induce secondary sexual characteristic development alongside possible fertility induction. [3]

For females, hormone replacement involves the use of oestrogen and progesterone. Firstly, oestrogen is used in tablet or gel form in order to maximise breast development, then a combination of oestrogen and progesterone is used. [3] [2] Cyclical progesterone is normally required to help keep the endometrium (lining of the uterus) healthy. [2]

In males, the monitoring of treatment normally requires the measurement of serum testosterone, inhibin B, haematocrit and prostate-specific antigen (PSA). If injections are used, trough levels are taken to ensure an adequate level of testosterone is achieved throughout the injection cycle. [3]

In females monitoring normally consists of measurement of oestrogen, FSH, LH, inhibin B and anti-Müllerian hormone (AMH). [3]

Standard hormone replacement therapy will not normally induce fertility in either males or females, with no testicular growth in males. Early treatment as adolescents can help with psychological well-being of people with KS/CHH. [3]

Fertility treatments

Gonadotropin therapy can be used in both male and female patients in order to achieve fertility for some people. [3] [2]

Pulsatile GnRH therapy can also be used to induce fertility, especially in females, but its use is limited to a few specialist treatment centres. [2]

In males with KS/CHH, infertility is primarily due to the lack of sperm production within the testes. Sperm production can be achieved through either the use of GnRH administered via a microinfusion pump or through the use of gonadotropin injections (hCG, FSH, hMG). The time taken to achieve adequate sperm production for natural conception will vary from person to person. If the pre-treatment testes are very small and there has been a history of undescended testes it might take longer to achieve sperm production. In these cases, assisted reproductive technology, such as sperm retrieval using testicular sperm extraction (TESE) and/or intracytoplasmic sperm injection (ICSI), might be required. [37]

In females with KS/CHH, infertility is primarily due to the lack of maturation of eggs located within the ovaries. Ovulation induction can be achieved either with pulsatile GnRH therapy or alternatively with gonadotropin injections (hCG, FSH, hMG) given at set intervals to trigger the maturation and release of the egg for natural conception. [37]

Prognosis

Reversal of symptoms has been reported in between 10% and 22% of cases. [38] [2]

Reversal cases have been seen in both KS and normosmic CHH but appear to be less common in cases of KS (where the sense of smell is also affected). Reversal is not always permanent and the precise genetic causes are not yet fully understood. [39]

Epidemiology

The epidemiology of Kallmann syndrome is not well understood. Individual studies include a 1986 report reviewing medical records in the Sardinian army which found a prevalence of 1 in 86,000 men [40] and a 2011 report from Finland which found a prevalence of 1:30,000 for males and 1:125,000 for females. [41]

Kallmann syndrome occurs about 4 times more often in males than females, but is only 2.5 times more common among males in familial cases. [40] [41]

History

Franz J. Kallmann, circa 1950 Franz J. Kallmann.jpg
Franz J. Kallmann, circa 1950

Kallmann syndrome was first described by name in a paper published in 1944 by Franz Josef Kallmann, a German-American geneticist. [7] [8] The link between anosmia and hypogonadism had already been noted by the Spanish doctor Aureliano Maestre de San Juan in 1856. [9] In the 1950s, De Morsier and Gauthier reported the partial or complete absence of the olfactory bulb in the brains of men with hypogonadism. [42] [10]

Terminology

The terminology used when describing cases of HH vary and can include:[ citation needed ]

Research

Kisspeptin is a protein that regulates the release of GnRH from the hypothalamus, which in turn regulates the release of LH and, to a lesser extent, FSH from the anterior pituitary gland. Kisspeptin and its associated receptor KISS1R are known to be involved in the regulation of puberty. Studies have shown there is potential for kisspeptin to be used in the diagnosis and treatment of certain cases of Kallmann syndrome and CHH. [44] [45]

Related Research Articles

<span class="mw-page-title-main">Luteinizing hormone</span> Gonadotropin secreted by the adenohypophysis

Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus. In females, an acute rise of LH known as an LH surge, triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone (ICSH), it stimulates Leydig cell production of testosterone. It acts synergistically with follicle-stimulating hormone (FSH).

<span class="mw-page-title-main">Follicle-stimulating hormone</span> Gonadotropin that regulates the development of reproductive processes

Follicle-stimulating hormone (FSH) is a gonadotropin, a glycoprotein polypeptide hormone. FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland and regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and luteinizing hormone (LH) work together in the reproductive system.

Delayed puberty is when a person lacks or has incomplete development of specific sexual characteristics past the usual age of onset of puberty. The person may have no physical or hormonal signs that puberty has begun. In the United States, girls are considered to have delayed puberty if they lack breast development by age 13 or have not started menstruating by age 15. Boys are considered to have delayed puberty if they lack enlargement of the testicles by age 14. Delayed puberty affects about 2% of adolescents.

Hypogonadism means diminished functional activity of the gonads—the testicles or the ovaries—that may result in diminished production of sex hormones. Low androgen levels are referred to as hypoandrogenism and low estrogen as hypoestrogenism. These are responsible for the observed signs and symptoms in both males and females.

Pubarche refers to the first appearance of pubic hair at puberty and it also marks the beginning of puberty. It is one of the physical changes of puberty and can occur independently of complete puberty. The early stage of sexual maturation, also known as adrenarche, is marked by characteristics including the development of pubic hair, axillary hair, adult apocrine body odor, acne, and increased oiliness of hair and skin. The Encyclopedia of Child and Adolescent Health corresponds SMR2 with pubarche, defining it as the development of pubic hair that occurs at a mean age of 11.6 years in females and 12.6 years in males. It further describes that pubarche's physical manifestation is vellus hair over the labia or the base of the penis. See Table 1 for the entirety of the sexual maturity rating description.

Gonadarche refers to the earliest gonadal changes of puberty. In response to pituitary gonadotropins, the ovaries in females and the testes in males begin to grow and increase the production of the sex steroids, especially estradiol and testosterone. The ovary and testis have receptors, follicle cells and leydig cells, respectively, where gonadotropins bind to stimulate the maturation of the gonads and secretion of estrogen and testosterone. Certain disorders can result in changes to timing or nature of these processes.

Isolated hypogonadotropic hypogonadism (IHH), also called idiopathic or congenital hypogonadotropic hypogonadism (CHH), as well as isolated or congenital gonadotropin-releasing hormone deficiency (IGD), is a condition which results in a small subset of cases of hypogonadotropic hypogonadism (HH) due to deficiency in or insensitivity to gonadotropin-releasing hormone (GnRH) where the function and anatomy of the anterior pituitary is otherwise normal and secondary causes of HH are not present.

<span class="mw-page-title-main">Gonadotropin-releasing hormone agonist</span> Drug class affecting sex hormones

A gonadotropin-releasing hormone agonist is a type of medication which affects gonadotropins and sex hormones. They are used for a variety of indications including in fertility medicine and to lower sex hormone levels in the treatment of hormone-sensitive cancers such as prostate cancer and breast cancer, certain gynecological disorders like heavy periods and endometriosis, high testosterone levels in women, early puberty in children, as a part of transgender hormone therapy, and to delay puberty in transgender youth among other uses. It is also used in the suppression of spontaneous ovulation as part of controlled ovarian hyperstimulation, an essential component in IVF. GnRH agonists are given by injections into fat, as implants placed into fat, and as nasal sprays.

The gonadotropin-releasing hormone receptor (GnRHR), also known as the luteinizing hormone releasing hormone receptor (LHRHR), is a member of the seven-transmembrane, G-protein coupled receptor (GPCR) family. It is the receptor of gonadotropin-releasing hormone (GnRH). The GnRHR is expressed on the surface of pituitary gonadotrope cells as well as lymphocytes, breast, ovary, and prostate.

Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a female, the testicles in a male. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed. Before puberty, the external sex organs, known as primary sexual characteristics, are sex characteristics that distinguish males and females. Puberty leads to sexual dimorphism through the development of the secondary sex characteristics, which further distinguish the sexes.

Hypergonadotropic hypogonadism (HH), also known as primary or peripheral/gonadal hypogonadism or primary gonadal failure, is a condition which is characterized by hypogonadism which is due to an impaired response of the gonads to the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), and in turn a lack of sex steroid production. As compensation and the lack of negative feedback, gonadotropin levels are elevated. Individuals with HH have an intact and functioning hypothalamus and pituitary glands so they are still able to produce FSH and LH. HH may present as either congenital or acquired, but the majority of cases are of the former nature. HH can be treated with hormone replacement therapy.

<span class="mw-page-title-main">Isolated 17,20-lyase deficiency</span> Medical condition

Isolated 17,20-lyase deficiency (ILD), also called isolated 17,20-desmolase deficiency, is a rare endocrine and autosomal recessive genetic disorder which is characterized by a complete or partial loss of 17,20-lyase activity and, in turn, impaired production of the androgen and estrogen sex steroids. The condition manifests itself as pseudohermaphroditism in males, in whom it is considered to be a form of intersex, and, in both sexes, as a reduced or absent puberty/lack of development of secondary sexual characteristics, resulting in a somewhat childlike appearance in adulthood.

<span class="mw-page-title-main">Leydig cell hypoplasia</span> Medical condition

Leydig cell hypoplasia (LCH), also known as Leydig cell agenesis, is a rare autosomal recessive genetic and endocrine syndrome affecting an estimated 1 in 1,000,000 genetic males. It is characterized by an inability of the body to respond to luteinizing hormone (LH), a gonadotropin which is normally responsible for signaling Leydig cells of the testicles to produce testosterone and other androgen sex hormones. The condition manifests itself as pseudohermaphroditism, hypergonadotropic hypogonadism, reduced or absent puberty, and infertility.

Gonadotropin-releasing hormone (GnRH) insensitivity also known as Isolated gonadotropin-releasing hormone (GnRH)deficiency (IGD) is a rare autosomal recessive genetic and endocrine syndrome which is characterized by inactivating mutations of the gonadotropin-releasing hormone receptor (GnRHR) and thus an insensitivity of the receptor to gonadotropin-releasing hormone (GnRH), resulting in a partial or complete loss of the ability of the gonads to synthesize the sex hormones. The condition manifests itself as isolated hypogonadotropic hypogonadism (IHH), presenting with symptoms such as delayed, reduced, or absent puberty, low or complete lack of libido, and infertility, and is the predominant cause of IHH when it does not present alongside anosmia.

Hypogonadotropic hypogonadism (HH), is due to problems with either the hypothalamus or pituitary gland affecting the hypothalamic-pituitary-gonadal axis. Hypothalamic disorders result from a deficiency in the release of gonadotropic releasing hormone (GnRH), while pituitary gland disorders are due to a deficiency in the release of gonadotropins from the anterior pituitary. GnRH is the central regulator in reproductive function and sexual development via the HPG axis. GnRH is released by GnRH neurons, which are hypothalamic neuroendocrine cells, into the hypophyseal portal system acting on gonadotrophs in the anterior pituitary. The release of gonadotropins, LH and FSH, act on the gonads for the development and maintenance of proper adult reproductive physiology. LH acts on Leydig cells in the male testes and theca cells in the female. FSH acts on Sertoli cells in the male and follicular cells in the female. Combined this causes the secretion of gonadal sex steroids and the initiation of folliculogenesis and spermatogenesis. The production of sex steroids forms a negative feedback loop acting on both the anterior pituitary and hypothalamus causing a pulsatile secretion of GnRH. GnRH neurons lack sex steroid receptors and mediators such as kisspeptin stimulate GnRH neurons for pulsatile secretion of GnRH.

Follicle-stimulating hormone (FSH) insensitivity, or ovarian insensitivity to FSH in females, also referable to as ovarian follicle hypoplasia or granulosa cell hypoplasia in females, is a rare autosomal recessive genetic and endocrine syndrome affecting both females and males, with the former presenting with much greater severity of symptomatology. It is characterized by a resistance or complete insensitivity to the effects of follicle-stimulating hormone (FSH), a gonadotropin which is normally responsible for the stimulation of estrogen production by the ovaries in females and maintenance of fertility in both sexes. The condition manifests itself as hypergonadotropic hypogonadism, reduced or absent puberty, amenorrhea, and infertility in females, whereas males present merely with varying degrees of infertility and associated symptoms.

Androgen deficiency is a medical condition characterized by insufficient androgenic activity in the body. Androgen deficiency most commonly affects women, and is also called Female androgen insufficiency syndrome (FAIS), although it can happen in both sexes. Androgenic activity is mediated by androgens, and is dependent on various factors including androgen receptor abundance, sensitivity and function. Androgen deficiency is associated with lack of energy and motivation, depression, lack of desire (libido), and in more severe cases changes in secondary sex characteristics.

<span class="mw-page-title-main">GnRH neuron</span>

GnRH neurons, or gonadotropin-releasing hormone expressing neurons, are the cells in the brain that control the release of reproductive hormones from the pituitary. These brain cells control reproduction by secreting GnRH into the hypophyseal portal capillary bloodstream, so are sometimes referred to as “sex neurons”. This small capillary network carries GnRH to the anterior pituitary, causing release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) into the wider bloodstream. When GnRH neurons change their pattern of release from the juvenile to the adult pattern of GnRH secretion, puberty is initiated. Failure of GnRH neurons to form the proper connections, or failure to successfully stimulate the pituitary with GnRH, means that puberty is not initiated. These disruptions to the GnRH system cause reproductive disorders like hypogonadotropic hypogonadism or Kallmann Syndrome.

<span class="mw-page-title-main">Fertile eunuch syndrome</span> Medical condition

The fertile eunuch syndrome or Pasqualini syndrome is a cause of hypogonadotropic hypogonadism caused by a luteinizing hormone deficiency. It is characterized by hypogonadism with spermatogenesis. Pasqualini and Bur published the first case of eunuchoidism with preserved spermatogenesis in 1950 in la Revista de la Asociación Médica Argentina. The hypoandrogenism with spermatogenesis syndrome included:

<span class="mw-page-title-main">Genetics of GnRH deficiency conditions</span>

To date, at least 25 different genes have been implicated in causing gonadotropin-releasing hormone (GnRH) deficiency conditions such as Kallmann syndrome (KS) or other forms of congenital hypogonadotropic hypogonadism (CHH) through a disruption in the production or activity of GnRH. These genes involved cover all forms of inheritance, and no one gene defect has been shown to be common to all cases, which makes genetic testing and inheritance prediction difficult.

References

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  6. ↑ Laitinen EM, Vaaralahti K, Tommiska J, Eklund E, Tervaniemi M, Valanne L, Raivio T (June 2011). "Incidence, phenotypic features and molecular genetics of Kallmann syndrome in Finland". Orphanet Journal of Rare Diseases. 6 (Jun 17): 41. doi: 10.1186/1750-1172-6-41 . PMC   3143089 . PMID   21682876.
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  35. ↑ Bouvattier C, Maione L, Bouligand J, Dodé C, Guiochon-Mantel A, Young J (October 2011). "Neonatal gonadotropin therapy in male congenital hypogonadotropic hypogonadism". Nature Reviews. Endocrinology. 8 (3): 172–82. doi:10.1038/nrendo.2011.164. PMID   22009162. S2CID   4564169.
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  40. 1 2 Tritos, Nicholas A (October 10, 2016). "Kallmann Syndrome and Idiopathic Hypogonadotropic Hypogonadism: Background, Pathophysiology, Epidemiology". eMedicine.{{cite journal}}: Cite journal requires |journal= (help)
  41. 1 2 Balasubramanian R, Crowley WF (March 2, 2017). "Isolated Gonadotropin-Releasing Hormone (GnRH) Deficiency". GeneReviews. University of Washington, Seattle. PMID   20301509.
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  44. ↑ Skorupskaite K, George JT, Anderson RA (2014). "The kisspeptin-GnRH pathway in human reproductive health and disease". Human Reproduction Update. 20 (4): 485–500. doi:10.1093/humupd/dmu009. PMC   4063702 . PMID   24615662.
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