What hormones does the thyroid gland synthesize?

The thyroid gland synthesizes and secretes T3, T4, and calcitonin. Thyroid hormones in the strict sense are thyroxine and triiodothyronine; they are iodinated derivatives of the amino acid tyrosine. The thyroid regulates metabolism and body growth, while calcitonin participates in regulating blood Ca2+ concentration.

What hormones are secreted by the adrenal cortex?

The adrenal cortex is the outer part of the adrenal gland and serves as the site of steroid synthesis. The general name for the products of the adrenal cortex is corticosteroids, with over 50 types described. Functionally, corticosteroids include precursors with low biological activity and true, life-essential hormones. Adrenal cortical hormones include glucocorticoids, mineralocorticoids, and androgenic hormones.

Where is the pineal gland anatomically located?

The pineal gland (corpus pineale, epiphysis) anatomically belongs to the epithalamus within the diencephalon and is located on the tectal plate (superior and inferior colliculi), which forms the roof of the midbrain. Topographically, this structure lies adjacent to the posterior wall of the third ventricle and serves as the posterior boundary of the diencephalon.

From which embryonic primordia does the pituitary gland form?

The pituitary gland has a dual embryonic origin and forms from two distinct primordia. The first is ectodermal and develops from an invagination of the oral ectoderm, forming Rathke's pouch, which gives rise to adenohypophyseal structures. The second is neural and develops as a downward outgrowth from the floor of the diencephalon's third ventricle, forming the neurohypophysis. The connective tissue of the pituitary derives from mesenchyme.

Which arteries supply the thyroid gland?

Blood supply to the thyroid gland is provided by branches of major neck vessels. These include the superior thyroid artery, arising near the origin of the external carotid artery and giving glandular branches to the lobes. Supply is also provided by the inferior thyroid artery from the thyrocervical trunk, which approaches the posterior surface of the gland and anastomoses with the superior thyroid artery.

What is the main anatomical difference between endocrine and exocrine glands?

Endocrine glands completely lack excretory ducts. They secrete their products directly into blood (venous) or lymphatic capillaries.

From which part of the brain do neurogenic endocrine glands develop?

The pituitary gland and pineal gland are genetically linked to the development of the diencephalon.

What ensures the rapid entry of hormones into the blood?

This is achieved because the tissue elements of the glands are permeated and wrapped by a dense network of blood and lymphatic vessels.

Home › Human Anatomy › Endocrine Glands

Endocrine Glands

Glandulae endocrinae

For medical students2 min readUpdated 2026-10-10

Endocrine glands (glandulae endocrinae) are specialized organs that lack excretory ducts and secrete their products (hormones) directly into the blood or lymphatic vessels. Due to a dense capillary network, active substances instantly enter the systemic circulation.

Main FeatureComplete absence of excretory ducts

Secretion PathwayHormones enter venous or lymphatic capillaries directly

EmbryogenesisDevelop from different germ layers (entoderm, mesoderm, and ectoderm)

Neurogenic GlandsClosely associated with the development of the diencephalon

Morphological Features

The key anatomical feature of endocrine glands is the absence of excretory ducts. The tissue elements of endocrine glands (glandulae endocrinae) are abundantly permeated and densely wrapped by a network of blood and lymphatic vessels.

Their secretion—hormones—bypasses any ducts and flows directly into venous or lymphatic capillaries. This intensive vascularization ensures the fastest possible entry of hormones into the body's general circulation.

List of Endocrine Glands

The organs of the endocrine system include the following glands:

Thyroid gland — glandula thyroidea
Parathyroid glands — glandulae parathyroideae
Thymus — thymus
Suprarenal (adrenal) glands — glandulae suprarenales
Paraganglia (chromaffin bodies) — paraganglia
Gonads: testes (testes) and ovaries (ovaria)
Pituitary gland — hypophysis (or glandula pituitaria)
Pineal gland — corpus pineale
Pancreas (endocrine part) — pancreas

Classification by Embryonic Origin

Despite close functional interdependence, endocrine organs have completely different embryonic origins. Based on genetic features, they are divided into several groups.

1. Endodermal Derivatives

Pharyngeal pouches: thyroid gland, parathyroid glands, and thymus.
Intestinal origin: endocrine part of the pancreas.

2. Mesodermal Derivatives Develop from the coelomic epithelium. This group includes the adrenal cortex and the endocrine portion of the gonads (testes and ovaries).

3. Ectodermal Derivatives

Sympathetic origin: adrenal medulla and paraganglia.
Neurogenic glands: pituitary gland and pineal gland. Their development is directly linked to the formation of the diencephalon.

Mnemonic

Note the adrenal glands (glandulae suprarenales): they have a dual origin. The cortex is derived from the mesoderm (like the gonads), while the medulla originates from the ectoderm (sympathetic origin).

Frequently asked questions

What hormones does the thyroid gland synthesize?: The thyroid gland synthesizes and secretes T3, T4, and calcitonin. Thyroid hormones in the strict sense are thyroxine and triiodothyronine; they are iodinated derivatives of the amino acid tyrosine. The thyroid regulates metabolism and body growth, while calcitonin participates in regulating blood Ca2+ concentration.
What hormones are secreted by the adrenal cortex?: The adrenal cortex is the outer part of the adrenal gland and serves as the site of steroid synthesis. The general name for the products of the adrenal cortex is corticosteroids, with over 50 types described. Functionally, corticosteroids include precursors with low biological activity and true, life-essential hormones. Adrenal cortical hormones include glucocorticoids, mineralocorticoids, and androgenic hormones.
Where is the pineal gland anatomically located?: The pineal gland (corpus pineale, epiphysis) anatomically belongs to the epithalamus within the diencephalon and is located on the tectal plate (superior and inferior colliculi), which forms the roof of the midbrain. Topographically, this structure lies adjacent to the posterior wall of the third ventricle and serves as the posterior boundary of the diencephalon.
From which embryonic primordia does the pituitary gland form?: The pituitary gland has a dual embryonic origin and forms from two distinct primordia. The first is ectodermal and develops from an invagination of the oral ectoderm, forming Rathke's pouch, which gives rise to adenohypophyseal structures. The second is neural and develops as a downward outgrowth from the floor of the diencephalon's third ventricle, forming the neurohypophysis. The connective tissue of the pituitary derives from mesenchyme.
Which arteries supply the thyroid gland?: Blood supply to the thyroid gland is provided by branches of major neck vessels. These include the superior thyroid artery, arising near the origin of the external carotid artery and giving glandular branches to the lobes. Supply is also provided by the inferior thyroid artery from the thyrocervical trunk, which approaches the posterior surface of the gland and anastomoses with the superior thyroid artery.
What is the main anatomical difference between endocrine and exocrine glands?: Endocrine glands completely lack excretory ducts. They secrete their products directly into blood (venous) or lymphatic capillaries.
From which part of the brain do neurogenic endocrine glands develop?: The pituitary gland and pineal gland are genetically linked to the development of the diencephalon.
What ensures the rapid entry of hormones into the blood?: This is achieved because the tissue elements of the glands are permeated and wrapped by a dense network of blood and lymphatic vessels.

Go deeper

Anatomy and Topography of the Thyroid Gland (glandula thyroidea)
Connection of the Pituitary Gland (hypophysis) with the Diencephalon
Structure of the Adrenal Glands: Cortex and Medulla
Endocrine Part of the Pancreas (pancreas)
Endocrine Function of the Gonads (testes, ovaria)