Endocrine Regulation, Pituitary Hormones, and Thyroid Anatomy

A comprehensive vocabulary review of the neuroendocrine regulation of antidiuretic hormone (ADH), anterior pituitary axes and their peripheral hormone targets, as well as the anatomical and histological organization of the thyroid and parathyroid glands.

Thirst center (hypothalamus)

A hypothalamic region stimulated by osmoreceptors in the hypothalamus and stretch-receptors in blood vessels to promote thirst and fluid intake.

Osmo-receptors in hypothalamus

Sensory receptors located within the hypothalamus that detect shifts in osmotic concentration and provide positive stimulatory input to both the thirst center and ADH-producing neurons.

Stretch-receptors in blood vessels

Mechanoreceptors located in vascular walls that monitor blood pressure and volume, sending positive regulatory signals to the hypothalamic thirst center and ADH-producing neurons.

ADH-producing neurons

Specialized hypothalamic neurosecretory cells that synthesize antidiuretic hormone and extend axons into the posterior pituitary for hormone storage and release.

Axon

The elongated neuronal process through which antidiuretic hormone is transported from hypothalamic neurosecretory cell bodies downward into the posterior pituitary.

Posterior pituitary

The neuroendocrine lobe of the pituitary gland that receives axon terminals from hypothalamic ADH-producing neurons and releases ADH directly into adjacent blood vessels.

ADH (Axonal neurosecretion)

Antidiuretic hormone packaged inside vesicles migrating down the neurosecretory axon toward terminal discharge sites in the posterior pituitary.

Antidiuretic hormone (ADH)

A neurohypophysial hormone secreted from posterior pituitary axon endings into the bloodstream to conserve water upon stimulation by osmoreceptors and stretch-receptors.

Anterior pituitary hormones

The collection of regulatory and tropic peptide hormones synthesized and secreted by the anterior pituitary, including FSH, LH, ACTH, TSH, GH, and Prolactin.

Testes

Male reproductive organs targeted by the anterior pituitary gonadotropins FSH and LH to stimulate the production of inhibin and testosterone, respectively.

Ovary

Female reproductive organs targeted by the anterior pituitary gonadotropins FSH and LH to stimulate the secretion of estradiol and progesterone, respectively.

Adrenal cortex

The outer portion of the adrenal gland targeted by adrenocorticotropic hormone (ACTH) to produce and release cortisol and corticosterone.

Thyroid gland (Endocrine target)

An endocrine gland stimulated by anterior pituitary thyroid-stimulating hormone (TSH) to produce and secrete thyroxine and triiodothyronine.

Liver and other tissues

Peripheral target tissues that respond to anterior pituitary growth hormone (GH) by synthesizing and releasing insulin-like growth factor 1 (IGF-1).

Mammary gland

Exocrine gland tissue in females targeted by anterior pituitary prolactin to stimulate milk synthesis.

IGF-1

Insulin-like growth factor 1, a hormone produced downstream by the liver and other tissues upon stimulation by growth hormone (GH).

Thyroxine and Triiodothyronine

Thyroid hormones synthesized and secreted by the thyroid gland following stimulation by thyroid-stimulating hormone (TSH).

Cortisol and Corticosterone

Glucocorticoid steroid hormones synthesized and secreted by the adrenal cortex in response to stimulation by ACTH.

Progesterone

A female steroid sex hormone secreted by the ovary following stimulation by luteinizing hormone (LH).

Testosterone

An androgenic steroid hormone produced and released by the testes upon stimulation by luteinizing hormone (LH).

Estradiol

An estrogen steroid hormone synthesized and secreted by the ovary upon stimulation by follicle-stimulating hormone (FSH).

Inhibin

A peptide hormone produced by the testes in response to follicle-stimulating hormone (FSH) that exerts negative feedback control on pituitary gonadotropin release.

Colloid

The proteinaceous, gel-like substance occupying the lumen of thyroid follicles, serving as a reservoir for thyroid hormone synthesis and storage.

Follicular cell

A cuboidal epithelial cell of the thyroid gland arranged in a single layer surrounding the central colloid, responsible for synthesizing thyroxine and triiodothyronine.

C-cell

A parafollicular endocrine cell located between thyroid follicles that secretes the calcium-lowering hormone calcitonin.

Jugular vein

A major cervical blood vessel positioned in the neck running lateral to the carotid artery and trachea, providing venous drainage from the head.

Thyroid gland (Cervical anatomy)

A bilobed endocrine gland situated on the ventrolateral aspects of the trachea in the neck, adjacent to the carotid artery, jugular vein, and parathyroid glands.

Carotid artery

A major systemic arterial vessel that courses through the neck adjacent to the trachea, jugular vein, and thyroid gland to supply oxygenated blood.

Trachea

The cartilaginous respiratory airway tube in the neck upon which the thyroid and parathyroid glands are physically situated.

Parathyroid glands

Small endocrine glands situated along or embedded within the thyroid gland tissue adjacent to the trachea, responsible for regulating calcium levels.