Endocrinology: The Hypothalamus and Pituitary Gland

Flashcards about the hypothalamus and pituitary gland

Hypothalamus

Region of the brain outside of the blood-brain barrier that receives sensory input and sends efferent output via the autonomic nervous system and pituitary gland.

Pituitary Gland

Divided into two parts: the posterior pituitary (neurohypophysis) which is nervous tissue, and the anterior pituitary (adenohypophysis) which is epithelial tissue.

Posterior Pituitary Gland Control

Nerve cell bodies in the hypothalamus are the site of hormone synthesis; axons run down the pituitary stalk to synapse on capillaries in the posterior pituitary, releasing hormones directly into the blood.

Anterior Pituitary Gland Control

No neural connection with the hypothalamus; capillary network (portal system) from the hypothalamus to the anterior pituitary gland; hormones secreted from nerves in the hypothalamus affect the secretion of hormones from endocrine cells in the anterior pituitary gland.

Antidiuretic Hormone (ADH)

Peptide hormone secreted in response to high blood osmolarity or low blood volume; reabsorbs water in the kidney and constricts blood vessels.

Oxytocin

Peptide hormone secreted in response to cervical stretch, suckling, or sexual intercourse; contracts smooth muscle in the uterus and ejects milk from mammary glands.

Adrenocorticotrophic Hormone (ACTH)

Secreted by pituitary corticotrophs in response to stress induced by corticotrophin-releasing hormone (CRH) from the hypothalamus; promotes growth and activity of the adrenal cortex, especially the secretion of glucocorticoids (cortisol).

Thyroid-Stimulating Hormone (TSH)

Glycoprotein secreted by pituitary thyrotrophs in response to cold induced by thyrotrophin-releasing hormone (TRH) from the hypothalamus; causes growth of the thyroid gland and secretion of thyroid hormones (thyroxine, triiodothyronine).

Growth Hormone (GH)

Protein hormone secreted by somatotrophs, especially during sleep and juvenile life, in response to GH-releasing hormone (GHRH) and inhibited by somatostatin from the hypothalamus; direct actions include amino acid uptake and protein synthesis, lipolysis, and glycogenolysis; indirect actions via IGFs include protein synthesis and growth of cartilage and bone.

Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH)

Glycoproteins secreted by gonadotrophs in response to gonadotrophin-releasing hormone (GnRH) from the hypothalamus; act on growth and activity of the ovary and testis.

Prolactin

Large polypeptide hormone secreted by lactotrophs, especially in pregnancy and lactation, and inhibited by dopamine from the hypothalamus; promotes growth of mammary glands and milk production.

Diabetes Insipidus

A disorder caused by defective ADH secretion from the posterior pituitary gland or defective ADH receptors in the kidney, leading to excess urine production (polyuria).

Acromegaly

A condition of GH excess.

Dwarfism

A condition of GH deficiency.