The zona fasciculata constitutes the middle zone of the adrenal cortex

Adrenal cortex

Situated along the perimeter of the adrenal gland, the adrenal cortex mediates the stress response through the production of mineralocorticoids and glucocorticoids, including aldosterone and cortisol respectively. It is also a secondary site of androgen synthesis.-Layers:Notably, the reticularis in...

, sitting directly beneath the zona glomerulosa

Zona glomerulosa

The zona glomerulosa of the adrenal gland is the most superficial layer of the adrenal cortex, lying directly beneath the adrenal gland's capsule...

. Constituent cells are organized into bundles or "fascicles".

The zona fasciculata chiefly produces glucocorticoids (mainly cortisol

Cortisol

Cortisol is a steroid hormone, more specifically a glucocorticoid, produced by the adrenal gland. It is released in response to stress and a low level of blood glucocorticoids. Its primary functions are to increase blood sugar through gluconeogenesis; suppress the immune system; and aid in fat,...

 in the human), which regulates the metabolism of glucose, especially in times of stress (e.g., part of the fight-or-flight response

Fight-or-flight response

The fight-or-flight response was first described by Walter Bradford Cannon....

), it is stimulated by the hormone Adrenocorticotropic Hormone

Adrenocorticotropic hormone

Adrenocorticotropic hormone , also known as 'corticotropin', 'Adrenocorticotrophic hormone', is a polypeptide tropic hormone produced and secreted by the anterior pituitary gland. It is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological...

 (ACTH) which is released from the anterior portion of the pituitary and axised upon this adrenal gland. This tissue also generates a small amount of weak androgen

Androgen

Androgen, also called androgenic hormone or testoid, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors...

s (e.g., dehydroepiandrosterone

Dehydroepiandrosterone

5-Dehydroepiandrosterone is a 19-carbon endogenous steroid hormone. It is the major secretory steroidal product of the adrenal glands and is also produced by the gonads and the brain. DHEA is the most abundant circulating steroid in humans....

). The main source of androgens will come from the zona reticularis

Zona reticularis

The zona reticularis 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 The zona reticularis is the innermost layer of the adrenal...

 region. In certain animals such as rodents, the lack of 17alpha-hydroxylase results in the synthesis of corticosterone

Corticosterone

Corticosterone is a 21-carbon steroid hormone of the corticosteroid type produced in the cortex of the adrenal glands.-Roles:In many species, including amphibians, reptiles, rodents and birds, corticosterone is a main glucocorticoid, involved in regulation of fuel, immune reactions, and stress...

 instead of cortisol.

Steroid-producing adrenal tumours and hyperplasia

Hyperplasia

Hyperplasia means increase in number of cells/proliferation of cells. It may result in the gross enlargement of an organ and the term is sometimes mixed with benign neoplasia/ benign tumor....

 of the zona fasciculata result in excess cortisol production and are the cause for adrenal Cushing's syndrome

Cushing's syndrome

Cushing's syndrome is a hormone disorder caused by high levels of cortisol in the blood. This can be caused by taking glucocorticoid drugs, or by tumors that produce cortisol or adrenocorticotropic hormone or CRH...

. The genetic disorder

Genetic disorder

A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....

 McCune-Albright syndrome

McCune-Albright syndrome

McCune–Albright syndrome, described in 1937 by Donovan James McCune and Fuller Albright, is a genetic disorder of bones, skin pigmentation and hormonal problems along with premature puberty.-Symptoms:...

can also present Cushing's syndrome in affected patients.