The adrenal cortex is the outer region and also the largest part of an
adrenal gland
The adrenal glands (also known as suprarenal 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 ...
. It is divided into three separate zones:
zona glomerulosa
The ''zona glomerulosa'' (sometimes, glomerular zone) 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 (''glomus'' is Latin ...
,
zona fasciculata
The ''zona fasciculata'' (sometimes, fascicular or fasciculate zone) 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 "fascicl ...
and
zona reticularis
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 ...
. Each zone is responsible for producing specific hormones. It is also a secondary site of
androgen
An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This inc ...
synthesis.
[ – "Adrenal Gland"]
Layers
The adrenal cortex comprises three main zones, or layers that are regulated by distinct hormones as noted below. This ''anatomic zonation'' can be appreciated at the microscopic level, where each zone can be recognized and distinguished from one another based on structural and anatomic characteristics.
;Zona glomerulosa
:The outermost layer, the
zona glomerulosa
The ''zona glomerulosa'' (sometimes, glomerular zone) 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 (''glomus'' is Latin ...
is the main site for the production of
aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
, a
mineralocorticoid
Mineralocorticoids are a class of corticosteroids, which in turn are a class of steroid hormones. Mineralocorticoids are produced in the adrenal cortex and influence salt and water balances (electrolyte balance and fluid balance). The primary mi ...
. The synthesis and secretion of aldosterone are mainly regulated by the
renin–angiotensin–aldosterone system. The zona glomerulosa cells express a specific enzyme
aldosterone synthase
Aldosterone synthase, also called steroid 18-hydroxylase, corticosterone 18-monooxygenase or P450C18, is a steroid hydroxylase cytochrome P450 enzyme involved in the biosynthesis of the mineralocorticoid aldosterone and other steroids. The enzyme ...
(also known as
CYP11B2).
Aldosterone is largely responsible for the long-term
regulation of blood pressure.
[Marieb Human Anatomy & Physiology 9th edition, chapter:16, page:629, question number:14] Aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
's effects are on the
distal convoluted tubule
The distal convoluted tubule (DCT) is a portion of kidney nephron between the loop of Henle and the collecting tubule.
Physiology
It is partly responsible for the regulation of potassium, sodium, calcium, and pH.
On its apical surface (lumen ...
and
collecting duct of the kidney where it causes increased reabsorption of sodium and increased excretion of both potassium (by principal cells) and hydrogen ions (by intercalated cells of the collecting duct).
Sodium retention is also a response of the distal colon, and sweat glands to aldosterone receptor stimulation. Although sustained production of aldosterone requires persistent
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
entry through low-voltage activated
Ca2+ channels, isolated zona glomerulosa cells are considered nonexcitable, with recorded membrane voltages that are too hyperpolarized to permit
Ca2+ channels entry.
:The secretion of aldosterone is also stimulated by
adrenocorticotropic hormone
Adrenocorticotropic hormone (ACTH; also adrenocorticotropin, corticotropin) 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 c ...
(ACTH).
:The expression of neuron-specific proteins in the zona glomerulosa cells of human adrenocortical tissues has been predicted and reported by several authors
and it was suggested that the expression of proteins like the
neuronal cell adhesion molecule (NCAM) in the cells of the zona glomerulosa reflects the regenerative feature of these cells, which would lose NCAM immunoreactivity after moving to the
zona fasciculata
The ''zona fasciculata'' (sometimes, fascicular or fasciculate zone) 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 "fascicl ...
.
However, together with other data on
neuroendocrine
Neuroendocrine cells are cells that receive neuronal input (through neurotransmitters released by nerve cells or neurosecretory cells) and, as a consequence of this input, release messenger molecules ( hormones) into the blood. In this way they b ...
properties of zona glomerulosa cells, NCAM expression may reflect a neuroendocrine differentiation of these cells.
;Zona fasciculata
:Situated between the glomerulosa and reticularis, the cells of the
zona fasciculata
The ''zona fasciculata'' (sometimes, fascicular or fasciculate zone) 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 "fascicl ...
synthesize and secrete
glucocorticoid
Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every vertebr ...
s, such as
11-deoxycorticosterone
11-Deoxycorticosterone (DOC), or simply deoxycorticosterone, also known as 21-hydroxyprogesterone, as well as desoxycortone (INN), deoxycortone, and cortexone, is a steroid hormone produced by the adrenal gland that possesses mineralocorticoid ac ...
,
corticosterone
Corticosterone, also known as 17-deoxycortisol and 11β,21-dihydroxyprogesterone, is a 21-carbon steroid hormone of the corticosteroid type produced in the cortex of the adrenal glands. It is of minor importance in humans, except in the very rare ...
, and
cortisol
Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone.
It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland ...
in humans. The major hormone that stimulates cortisol secretion in humans is the ACTH that is released from the
anterior pituitary
A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular, anterior lobe that together with the posterior lobe (posterior pituitary, or the neurohypophysis) makes up the p ...
.
It has been shown that the steroidogenic capacity of the zona fasciculata increases during illness in infants.
;Zona reticularis
:The inner most cortical layer, the
zona reticularis
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 ...
produces
androgen
An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This inc ...
s, mainly
dehydroepiandrosterone
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 fun ...
(DHEA),
DHEA sulfate
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 dehydroep ...
(DHEA-S), and
androstenedione (the precursor to
testosterone
Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
) in humans. The secretion of DHEAS is also stimulated by ACTH.
Hormone synthesis
![Adrenal Steroids Pathways - edited](https://upload.wikimedia.org/wikipedia/commons/a/a6/Adrenal_Steroids_Pathways_-_edited.svg)
The precursor of steroids synthesized in the adrenal cortex is
cholesterol
Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...
that is stored in vesicles. Cholesterol can be synthesized
de novo in the adrenal cortex. Yet, the major source of cholesterol appears to be cholesterol that is taken up with circulating lipoproteins.
The steps up to this point occur in many
steroid
A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...
-producing tissues. Subsequent steps to generate aldosterone and cortisol, however, primarily occur in the adrenal cortex:
* Progesterone → (hydroxylation at C21) → 11-
Deoxycorticosterone Deoxycorticosterone (DOC), or desoxycorticosterone, may refer to:
* 11-Deoxycorticosterone (21-hydroxyprogesterone)
* 21-Deoxycorticosterone (11β-hydroxyprogesterone)
See also
* Deoxycortisol
* Deoxycortisone
* 11-Hydroxyprogesterone
{{Che ...
→ (two further hydroxylations at C11 and C18) →
Aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
* Progesterone → (hydroxylation at C17) → 17-alpha-hydroxyprogesterone → (hydroxylation at C21) →
11-Deoxycortisol → (hydroxylation at C11) →
Cortisol
Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone.
It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland ...
Production
The adrenal cortex produces a number of different
corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
s.
Mineralocorticoids
The primary
mineralocorticoid
Mineralocorticoids are a class of corticosteroids, which in turn are a class of steroid hormones. Mineralocorticoids are produced in the adrenal cortex and influence salt and water balances (electrolyte balance and fluid balance). The primary mi ...
,
aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
, is produced in the adrenocortical
zona glomerulosa
The ''zona glomerulosa'' (sometimes, glomerular zone) 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 (''glomus'' is Latin ...
by the action of the enzyme
aldosterone synthase
Aldosterone synthase, also called steroid 18-hydroxylase, corticosterone 18-monooxygenase or P450C18, is a steroid hydroxylase cytochrome P450 enzyme involved in the biosynthesis of the mineralocorticoid aldosterone and other steroids. The enzyme ...
(also known as
CYP11B2).
Aldosterone is largely responsible for the long-term
regulation of blood pressure.
Aldosterone effects on the
distal convoluted tubule
The distal convoluted tubule (DCT) is a portion of kidney nephron between the loop of Henle and the collecting tubule.
Physiology
It is partly responsible for the regulation of potassium, sodium, calcium, and pH.
On its apical surface (lumen ...
and
collecting duct of the kidney where it causes increased reabsorption of sodium and increased excretion of both potassium (by principal cells) and hydrogen ions (by intercalated cells of the collecting duct).
Sodium retention is also a response of the distal colon, and sweat glands to aldosterone receptor stimulation. Although sustained production of aldosterone requires persistent
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
entry through low-voltage activated
Ca2+ channels, isolated zona glomerulosa cells are considered nonexcitable, with recorded membrane voltages that are too hyperpolarized to permit
Ca2+ channels entry.
Glucocorticoids
Glucocorticoids are produced in the
zona fasciculata
The ''zona fasciculata'' (sometimes, fascicular or fasciculate zone) 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 "fascicl ...
. The primary glucocorticoid released by the adrenal gland is
cortisol
Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone.
It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland ...
in humans and
corticosterone
Corticosterone, also known as 17-deoxycortisol and 11β,21-dihydroxyprogesterone, is a 21-carbon steroid hormone of the corticosteroid type produced in the cortex of the adrenal glands. It is of minor importance in humans, except in the very rare ...
in many other animals. Its secretion is regulated by the hormone
ACTH
Adrenocorticotropic hormone (ACTH; also adrenocorticotropin, corticotropin) 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 c ...
from the
anterior pituitary
A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular, anterior lobe that together with the posterior lobe (posterior pituitary, or the neurohypophysis) makes up the p ...
.
Androgens
They are produced in the
zona reticularis
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 ...
. The most important androgens include:
*
Testosterone
Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
: a hormone with a wide variety of effects, ranging from enhancing muscle mass and stimulation of
cell growth
Cell growth refers to an increase in the total mass of a cell, including both cytoplasmic, nuclear and organelle volume. Cell growth occurs when the overall rate of cellular biosynthesis (production of biomolecules or anabolism) is greater than ...
to the development of the
secondary sex characteristic
Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a sp ...
s.
*
Dihydrotestosterone
Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous androgen sex steroid and hormone. The enzyme 5α-reductase catalyzes the formation of DHT from testosterone in certain tissues includi ...
(DHT): a
metabolite
In biochemistry, a metabolite is an intermediate or end product of metabolism.
The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
of testosterone, and a more potent androgen than testosterone in that it binds more strongly to androgen receptors.
*
Androstenedione (Andro): an androgenic steroid produced by the
testes
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoster ...
, adrenal cortex, and
ovaries
The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...
. While
androstenediones are converted metabolically to testosterone and other
androgen
An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This inc ...
s, they are also the parent structure of
estrone
Estrone (E1), also spelled oestrone, is a steroid, a weak estrogen, and a minor female sex hormone. It is one of three major endogenous estrogens, the others being estradiol and estriol. Estrone, as well as the other estrogens, are synthesized ...
.
*
Dehydroepiandrosterone
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 fun ...
(DHEA): It is the primary precursor of natural
estrogen
Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
s. DHEA is also called
dehydroisoandrosterone
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 func ...
or
dehydroandrosterone
Dehydroandrosterone (DHA), or 5-dehydroandrosterone (5-DHA), also known as isoandrostenolone, as well as androst-5-en-3α-ol-17-one, is an endogenous androgen steroid hormone. It is the 3α-epimer of dehydroepiandrosterone (DHEA; androst-5-en-3Π...
. The reticularis also produces
DHEA-sulfate due to the actions of a
sulfotransferase
Sulfotransferases (SULTs) are transferase enzymes that catalyze the transfer of a sulfo group from a donor molecule to an acceptor alcohol or amine. The most common sulfo group donor is 3'-phosphoadenosine-5'-phosphosulfate (PAPS). In the case o ...
,
SULT2A1
Bile salt sulfotransferase also known as hydroxysteroid sulfotransferase (HST) or sulfotransferase 2A1 (ST2A1) is an enzyme that in humans is encoded by the ''SULT2A1'' gene.
Function
Sulfotransferase enzymes catalyze the sulfate conjugation ...
.
Pathology
*
Adrenal insufficiency (e.g. due to
Addison's disease
Addison's disease, also known as primary adrenal insufficiency, is a rare long-term endocrine disorder characterized by inadequate production of the steroid hormones cortisol and aldosterone by the two outer layers of the cells of the adre ...
)
*
Cushing's syndrome
Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, a ...
*
Cushing's disease
Cushing's disease is one cause of Cushing's syndrome characterised by increased secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary (secondary hypercortisolism). This is most often as a result of a pituitary adenoma (spe ...
*
Conn's syndrome
Primary aldosteronism (PA)'','' also known as primary hyperaldosteronism or Conn's syndrome, refers to the excess production of the hormone aldosterone from the adrenal glands, resulting in low renin levels and high blood pressure. This abnormalit ...
*
Adrenocortical carcinoma
Adrenocortical carcinoma (ACC) is an aggressive cancer originating in the cortex (steroid hormone-producing tissue) of the adrenal gland.
Adrenocortical carcinoma is remarkable for the many hormonal syndromes that can occur in patients with ste ...
See also
*
Adrenarche
Adrenarche is an early stage in sexual maturation that happens in some higher primates and in humans, typically peaks at around 20 years of age, and is involved in the development of pubic hair, body odor, skin oiliness, axillary hair, sexual ...
*
Adrenopause
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 ...
References
External links
* – "Posterior Abdominal Wall: Blood Supply to the Suprarenal Glands"
*
*
{{DEFAULTSORT:Adrenal Cortex
Adrenal gland