Zona reticularis

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Zona reticularis
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Layers of cortex.
Details
Identifiers
Latin zona reticularis
MeSH D015385
FMA 69236
Anatomical terminology

The zona reticularis (sometimes, reticulate zone) is the innermost layer of the adrenal cortex, lying deep to the zona fasciculata and superficial to the adrenal medulla. The cells are arranged cords that project in different directions giving a net-like appearance (L. reticulum - net). [1]

Cells in the zona reticularis produce precursor androgens including dehydroepiandrosterone (DHEA) and androstenedione from cholesterol. [2] DHEA is further converted to DHEA-sulfate via a sulfotransferase, SULT2A1. [3] These precursors are not further converted in the adrenal cortex if the cells lack 17β-Hydroxysteroid dehydrogenase. Instead, they are released into the blood stream and taken up in the testicles and ovaries to produce testosterone and the estrogens respectively.

ACTH partially regulates adrenal androgen secretion, [4] also CRH. [5] [6]

In humans, the reticularis layer does contain 17α-hydroxylase; this hydroxylates pregnenolone, which is then converted to cortisol by a mixed function oxidase. In rodents, the lack of 17α-hydroxylase results in the synthesis of corticosterone instead of cortisol as in the human.[ citation needed ]

Adrenal gland (zona reticularis layer). Adrenal gland (zona reticularis).JPG
Adrenal gland (zona reticularis layer).

Related Research Articles

<span class="mw-page-title-main">Adrenal gland</span> Endocrine gland

The adrenal glands are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex which produces steroid hormones and an inner medulla. The adrenal cortex itself is divided into three main zones: the zona glomerulosa, the zona fasciculata and the zona reticularis.

<span class="mw-page-title-main">Dehydroepiandrosterone</span> Chemical compound

Dehydroepiandrosterone (DHEA), also known as androstenolone, is an endogenous steroid hormone precursor. It is one of the most abundant circulating steroids in humans. DHEA is produced in the adrenal glands, the gonads, and the brain. It functions as a metabolic intermediate in the biosynthesis of the androgen and estrogen sex steroids both in the gonads and in various other tissues. However, DHEA also has a variety of potential biological effects in its own right, binding to an array of nuclear and cell surface receptors, and acting as a neurosteroid and modulator of neurotrophic factor receptors.

<span class="mw-page-title-main">Adrenocorticotropic hormone</span> Pituitary hormone

Adrenocorticotropic hormone is a polypeptide tropic hormone produced by and secreted by the anterior pituitary gland. It is also used as a medication and diagnostic agent. ACTH is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological stress. Its principal effects are increased production and release of cortisol and androgens by the zona fasiculata and zona reticularis, respectively. ACTH is also related to the circadian rhythm in many organisms.

<span class="mw-page-title-main">Androgen</span> Any steroid hormone that promotes male characteristics

An androgen is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes the embryological development of the primary male sex organs, and the development of male secondary sex characteristics at puberty. Androgens are synthesized in the testes, the ovaries, and the adrenal glands.

<span class="mw-page-title-main">Adrenal cortex</span> Cortex of the adrenal gland

The adrenal cortex is the outer region and also the largest part of the adrenal gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. It is also a secondary site of androgen synthesis.

<span class="mw-page-title-main">Congenital adrenal hyperplasia</span> Medical condition

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders characterized by impaired cortisol synthesis. It results from the deficiency of one of the five enzymes required for the synthesis of cortisol in the adrenal cortex. Most of these disorders involve excessive or deficient production of hormones such as glucocorticoids, mineralocorticoids, or sex steroids, and can alter development of primary or secondary sex characteristics in some affected infants, children, or adults. It is one of the most common autosomal recessive disorders in humans.

<span class="mw-page-title-main">Adrenal insufficiency</span> Medical condition

Adrenal insufficiency is a condition in which the adrenal glands do not produce adequate amounts of steroid hormones. The adrenal glands—also referred to as the adrenal cortex—normally secrete glucocorticoids, mineralocorticoids, and androgens. These hormones are important in regulating blood pressure, electrolytes, and metabolism as a whole. Deficiency of these hormones leads to symptoms ranging from abdominal pain, vomiting, muscle weakness and fatigue, low blood pressure, depression, mood and personality changes to organ failure and shock. Adrenal crisis may occur if a person having adrenal insufficiency experiences stresses, such as an accident, injury, surgery, or severe infection; this is a life-threatening medical condition resulting from severe deficiency of cortisol in the body. Death may quickly follow.

<span class="mw-page-title-main">Congenital adrenal hyperplasia due to 3β-hydroxysteroid dehydrogenase deficiency</span> Medical condition

Congenital adrenal hyperplasia due to 3β-hydroxysteroid dehydrogenase deficiency is an uncommon form of congenital adrenal hyperplasia (CAH) resulting from a mutation in the gene for one of the key enzymes in cortisol synthesis by the adrenal gland, 3β-hydroxysteroid dehydrogenase (3β-HSD) type II (HSD3B2). As a result, higher levels of 17α-hydroxypregnenolone appear in the blood with adrenocorticotropic hormone (ACTH) challenge, which stimulates adrenal corticosteroid synthesis.

Congenital adrenal hyperplasia due to 17α-hydroxylase deficiency is an uncommon form of congenital adrenal hyperplasia (CAH) resulting from a mutation in the gene CYP17A1, which produces the enzyme 17α-hydroxylase. It causes decreased synthesis of cortisol and sex hormones, with resulting increase in mineralocorticoid production. Thus, common symptoms include mild cortisol deficiency, ambiguous genitalia in men or amenorrhea at puberty in women, and hypokalemic hypertension. However, partial (incomplete) deficiency often has inconsistent symptoms between patients, and affected women may be asymptomatic except for infertility.

Adrenarche is an early stage in sexual maturation that happens in some higher primates, typically peaks at around 20 years of age, and is involved in the development of pubic hair, body odor, skin oiliness, axillary hair, sexual attraction/sexual desire/increased libido and mild acne. During adrenarche the adrenal glands secrete increased levels of weak adrenal androgens, including dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), and androstenedione (A4), but without increased cortisol levels. Adrenarche is the result of the development of a new zone of the adrenal cortex, the zona reticularis. Adrenarche is a process related to puberty, but distinct from hypothalamic–pituitary–gonadal axis maturation and function.

<span class="mw-page-title-main">Pregnenolone</span> Chemical compound

Pregnenolone (P5), or pregn-5-en-3β-ol-20-one, is an endogenous steroid and precursor/metabolic intermediate in the biosynthesis of most of the steroid hormones, including the progestogens, androgens, estrogens, glucocorticoids, and mineralocorticoids. In addition, pregnenolone is biologically active in its own right, acting as a neurosteroid.

<span class="mw-page-title-main">17α-Hydroxyprogesterone</span> Chemical compound

17α-Hydroxyprogesterone (17α-OHP), also known as 17-OH progesterone (17-OHP), or hydroxyprogesterone (OHP), is an endogenous progestogen steroid hormone related to progesterone. It is also a chemical intermediate in the biosynthesis of many other endogenous steroids, including androgens, estrogens, glucocorticoids, and mineralocorticoids, as well as neurosteroids.

<span class="mw-page-title-main">Zona glomerulosa</span> Part of the adrenal gland

The zona glomerulosa of the adrenal gland is the most superficial layer of the adrenal cortex, lying directly beneath the renal capsule. Its cells are ovoid and arranged in clusters or arches.

<span class="mw-page-title-main">Zona fasciculata</span>

The zona fasciculata constitutes the middle and also the widest zone of the adrenal cortex, sitting directly beneath the zona glomerulosa. Constituent cells are organized into bundles or "fascicles".

In humans and other animals, the adrenocortical hormones are hormones produced by the adrenal cortex, the outer region of the adrenal gland. These polycyclic steroid hormones have a variety of roles that are crucial for the body's response to stress, and they also regulate other functions in the body. Threats to homeostasis, such as injury, chemical imbalances, infection, or psychological stress, can initiate a stress response. Examples of adrenocortical hormones that are involved in the stress response are aldosterone and cortisol. These hormones also function in regulating the conservation of water by the kidneys and glucose metabolism, respectively.

<span class="mw-page-title-main">Dehydroepiandrosterone sulfate</span> Chemical compound

Dehydroepiandrosterone sulfate, abbreviated as DHEA sulfate or DHEA-S, also known as androstenolone sulfate, is an endogenous androstane steroid that is produced by the adrenal cortex. It is the 3β-sulfate ester and a metabolite of dehydroepiandrosterone (DHEA) and circulates in far greater relative concentrations than DHEA. The steroid is hormonally inert and is instead an important neurosteroid and neurotrophin.

<span class="mw-page-title-main">CYP17A1</span> Mammalian protein found in Homo sapiens

Cytochrome P450 17A1 is an enzyme of the hydroxylase type that in humans is encoded by the CYP17A1 gene on chromosome 10. It is ubiquitously expressed in many tissues and cell types, including the zona reticularis and zona fasciculata of the adrenal cortex as well as gonadal tissues. It has both 17α-hydroxylase and 17,20-lyase activities, and is a key enzyme in the steroidogenic pathway that produces progestins, mineralocorticoids, glucocorticoids, androgens, and estrogens. More specifically, the enzyme acts upon pregnenolone and progesterone to add a hydroxyl (-OH) group at carbon 17 position (C17) of the steroid D ring, or acts upon 17α-hydroxyprogesterone and 17α-hydroxypregnenolone to split the side-chain off the steroid nucleus.

3β-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3β-HSD) is an enzyme that catalyzes the biosynthesis of the steroid progesterone from pregnenolone, 17α-hydroxyprogesterone from 17α-hydroxypregnenolone, and androstenedione from dehydroepiandrosterone (DHEA) in the adrenal gland. It is the only enzyme in the adrenal pathway of corticosteroid synthesis that is not a member of the cytochrome P450 family. It is also present in other steroid-producing tissues, including the ovary, testis and placenta. In humans, there are two 3β-HSD isozymes encoded by the HSD3B1 and HSD3B2 genes.

<span class="mw-page-title-main">Steroid 11β-hydroxylase</span> Protein found in mammals

Steroid 11β-hydroxylase, also known as steroid 11β-monooxygenase, is a steroid hydroxylase found in the zona glomerulosa and zona fasciculata of the adrenal cortex. Named officially the cytochrome P450 11B1, mitochondrial, it is a protein that in humans is encoded by the CYP11B1 gene. The enzyme is involved in the biosynthesis of adrenal corticosteroids by catalyzing the addition of hydroxyl groups during oxidation reactions.

<span class="mw-page-title-main">Adrenopause</span> Decline in secretion and levels of adrenal androgens

Adrenopause is the decline in secretion and levels of adrenal androgens such as dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S) from the zona reticularis of the adrenal glands with age. Levels of adrenal androgens start to increase around age 7 or 8 years (adrenarche), peak in early adulthood around age 20 to 25 years, and decrease at a rate of approximately 2% per year thereafter, eventually reaching levels of 10 to 20% of those of young adults by age 80 years. It is caused by the progressive apoptosis of adrenal androgen-secreting cells and hence involution of the zona reticularis. It is analogous to andropause in men and menopause in women, the abrupt or gradual decline in production of sex hormones from the gonads with age.

References

  1. Histology: A Text and Atlas, 5th ed. Ross and Pawlina.[ page needed ]
  2. Wheater's Functional Histology, 5th ed. Young, Lowe, Stevens and Heath.[ page needed ]
  3. Rainey WE, Nakamura Y (February 2008). "Regulation of the Adrenal Androgen Biosynthesis". J. Steroid Biochem. Mol. Biol. 108 (3–5): 281–6. doi:10.1016/j.jsbmb.2007.09.015. PMC   2699571 . PMID   17945481.
  4. Pediatric Adrenal Insufficiency (Addison Disease) at eMedicine
  5. Ibáñez L, Potau N, Marcos MV, de Zegher F (September 1999). "Corticotropin-releasing hormone as adrenal androgen secretagogue". Pediatric Research. 46 (3): 351–3. doi: 10.1203/00006450-199909000-00018 . PMID   10473054.
  6. Coppola, Christopher P.; Merrell, Ronald C. (2001). "Neoplasms of the Adrenal and Endocrine Pancreas in the Elderly". In Rosenthal, Ronnie A.; Zenilman, Michael E.; Katlic, Mark R. (eds.). Principles and Practice of Geriatric Surgery. Springer. pp. 301–21. doi:10.1007/978-1-4757-3432-4_22. ISBN   978-1-4757-3432-4.