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 w ...

. It is divided into three separate zones: zona glomerulosa, zona fasciculata 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 in ...

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 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

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 ...

. 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 (also known as

CYP11B2 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 ...

). Aldosterone is largely responsible for the long-term

regulation of blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...

.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 ...

'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 t ...

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 (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. 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 br ...

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 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 verte ...

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 mineralocorticoi ...

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 ra ...

, 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 g ...

in humans. The major hormone that stimulates cortisol secretion in humans is the ACTH that is released from the anterior pituitary. 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

produces

s, mainly dehydroepiandrosterone (DHEA), DHEA sulfate (DHEA-S), and

androstenedione Androstenedione, or 4-androstenedione (abbreviated as A4 or Δ4-dione), also known as androst-4-ene-3,17-dione, is an endogenous weak androgen steroid hormone and intermediate in the biosynthesis of estrone and of testosterone from dehy ...

(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 tissues such as testes and prostate, as well as promoting secondary sexual characteris ...

) in humans. The secretion of DHEAS is also stimulated by ACTH.

Hormone synthesis

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 membr ...

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 ...

-producing tissues. Subsequent steps to generate aldosterone and cortisol, however, primarily occur in the adrenal cortex: * Progesterone → (hydroxylation at C21) → 11- Deoxycorticosterone → (two further hydroxylations at C11 and C18) →

* Progesterone → (hydroxylation at C17) → 17-alpha-hydroxyprogesterone → (hydroxylation at C21) →

11-Deoxycortisol 11-Deoxycortisol, also known as cortodoxone (INN), cortexolone as well as 17α,21-dihydroxyprogesterone or 17α,21-dihydroxypregn-4-ene-3,20-dione, is an endogenous glucocorticoid steroid hormone, and a metabolic intermediate towards cortisol. I ...

→ (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 g ...

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 in ...

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 ...

Mineralocorticoids

The primary

, is produced in the adrenocortical zona glomerulosa by the action of the enzyme aldosterone synthase (also known as

). Aldosterone is largely responsible for the long-term

. Aldosterone effects on the

Glucocorticoids

Glucocorticoids are produced in the zona fasciculata. The primary glucocorticoid released by the adrenal gland is

in humans and

in many other animals. Its secretion is regulated by the hormone ACTH from the anterior pituitary.

Androgens

They are produced in the

. 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 tissues such as testes and prostate, as well as promoting secondary sexual characteris ...

: a hormone with a wide variety of effects, ranging from enhancing muscle mass and stimulation of cell growth 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 ...

s. * Dihydrotestosterone (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, ...

of testosterone, and a more potent androgen than testosterone in that it binds more strongly to androgen receptors. *

Androstenedione Androstenedione, or 4-androstenedione (abbreviated as A4 or Δ4-dione), also known as androst-4-ene-3,17-dione, is an endogenous weak androgen steroid hormone and intermediate in the biosynthesis of estrone and of testosterone from dehy ...

(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 testostero ...

, adrenal cortex, and ovaries. While

s are converted metabolically to testosterone and other

s, they are also the parent structure of estrone. * Dehydroepiandrosterone (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 a ...

s. DHEA is also called dehydroisoandrosterone or dehydroandrosterone. The reticularis also produces DHEA-sulfate due to the actions of a sulfotransferase, SULT2A1.

Pathology

Adrenal insufficiency Adrenal insufficiency is a condition in which the adrenal glands do not produce adequate amounts of steroid hormones. The adrenal gland normally secretes glucocorticoids (primarily cortisol), mineralocorticoids (primarily aldosterone), and androge ...

(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 adrena ...

) * Cushing's syndrome *

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 (s ...

* Conn's syndrome * Adrenocortical carcinoma

References

External links

* – "Posterior Abdominal Wall: Blood Supply to the Suprarenal Glands" * * {{DEFAULTSORT:Adrenal Cortex Adrenal gland