Pituitary Gland and Hypothalamic Hormones

Comprehensive vocabulary flashcards covering the anterior pituitary hormones, actions and regulation of growth hormone and prolactin, and clinical conditions including dwarfism, gigantism, acromegaly, Sheehan's syndrome, and hyperprolactinemia.

Adenohypophysis

The anterior lobe of the pituitary gland, responsible for synthesizing and secreting trophic hormones including GH, TSH, ACTH, FSH, LH, and PRL.

Acidophilic Cells

A category of chromophilic secretory cells in the anterior pituitary that stain with acid dyes and secrete Growth Hormone (GH) and Prolactin (PRL).

Basophilic Cells

A category of chromophilic secretory cells in the anterior pituitary that stain with basic dyes and secrete FSH, LH, ACTH, and TSH (B-FLAT).

Somatotropes

Anterior pituitary acidophilic cells that synthesize and secrete Growth Hormone (somatotropin).

Lactotropes

Also called mammotropes; anterior pituitary acidophilic cells that secrete Prolactin.

Pro-opiomelanocortin (POMC)

A large precursor polypeptide produced in the anterior and intermediate lobes of the pituitary that is cleaved to form ACTH and MSH.

Albinism

A congenital disorder characterized by the inability to synthesize melanin due to a genetic defect in the enzyme tyrosinase, which converts tyrosine into melanin pigment.

Vitiligo

A progressive skin condition characterized by an acquired loss of melanin after birth, linked to autoimmune mechanisms, physical trauma, or environmental factors.

Growth Hormone (Somatotropin / STH)

A single-chain polypeptide hormone released in a pulsatile manner by the anterior pituitary that acts via cell membrane receptors coupled to a tyrosine kinase second messenger system.

Growth Hormone-Releasing Hormone (GHRH)

A hypothalamic peptide hormone that stimulates the synthesis and secretion of Growth Hormone from anterior pituitary somatotropes.

Somatostatin (GHIH)

A hypothalamic hormone (Growth Hormone-Inhibiting Hormone / SRIF) that inhibits Growth Hormone secretion by blocking the anterior pituitary's response to GHRH.

Somatomedins (IGF)

Polypeptides synthesized predominantly in the liver (as well as kidneys, cartilage, and muscle) in response to GH that mediate the indirect anabolic and skeletal actions of Growth Hormone.

Somatomedin C (IGF-1)

The primary circulating insulin-like growth factor in humans that stimulates chondrogenesis, osteoblast appearance, and protein synthesis, while declining with advanced age.

Diabetogenic Effect of GH

A direct action of Growth Hormone that raises blood glucose levels (hyperglycemia) by increasing hepatic glucose output and decreasing peripheral glucose utilization (anti-insulin effect).

Ketogenic Effect of GH

A direct catabolic effect of Growth Hormone that mobilizes adipose tissue triglycerides via lipolysis, generating free fatty acids (FFAs) that undergo hepatic oxidation into ketone bodies.

Pituitary Dwarfism

A condition caused by Growth Hormone or GHRH deficiency during childhood, characterized by stunted linear growth with body proportions appropriate for chronological age, plumpness, immature facies, normal intelligence, and hypoglycemia.

Cretinism (Hypothyroid Dwarfism)

A form of dwarfism resulting from congenital thyroid hormone deficiency, characterized by infantile body proportions, severe mental retardation, and gross physical developmental delay.

Laron Dwarfism

A form of dwarfism caused by defective Growth Hormone receptors (GH insensitivity), characterized by elevated circulating levels of GH and GHRH, but markedly reduced levels of IGF-1.

Gigantism

A condition resulting from excessive Growth Hormone secretion during adolescence before epiphyseal plate closure, causing accelerated linear growth of long bones, extreme height (up to $8\,\text{ft}$ / $2.5\,\text{m}$), bilateral gynaecomastia, and coarse facial features.

Acromegaly

A condition caused by excessive Growth Hormone secretion in adulthood after epiphyseal plate closure, characterized by periosteal bone thickening, acral enlargement, visceromegaly, and acromegalic facies.

Prognathism

The elongation, widening, and forward protrusion of the mandible, characteristically seen in patients with acromegaly.

Acromegalic Facies

The coarse facial appearance in acromegaly produced by soft-tissue and connective-tissue proliferation, characterized by a prominent brow, bulbous nose, thickened skin, and facial edema.

Octreotide

A synthetic somatostatin analogue used medically to treat Growth Hormone excess (such as acromegaly) by inhibiting pituitary GH secretion.

Sheehan's Syndrome

Postpartum ischemic necrosis and infarction of the physiologically enlarged anterior pituitary following severe postpartum hemorrhage, resulting in panhypopituitarism (failure to lactate, amenorrhea, hypothyroidism) while sparing posterior pituitary function.

Panhypopituitarism

The deficiency or complete loss of secretion of all anterior pituitary trophic hormones.

Prolactin (PRL)

A single-chain anterior pituitary polypeptide hormone that stimulates mammary gland development and lactogenesis (milk production) and inhibits GnRH release.

Lactational Amenorrhea

The physiological suppression of menstruation during lactation, occurring because elevated Prolactin inhibits hypothalamic GnRH release, which decreases pituitary LH and FSH and prevents ovulation.

Prolactin-Inhibiting Factor (PIF)

Hypothalamic dopamine, which exerts continuous tonic negative inhibitory control over Prolactin secretion by anterior pituitary lactotropes.

Galactogogues

Substances that increase milk production and secretion by promoting Prolactin release, including dopamine (PIF) antagonists and TRH analogues.

Hyperprolactinemia

Elevated circulating prolactin levels caused by prolactinomas, stalk lesions, or dopamine antagonists, clinically manifesting with galactorrhea, amenorrhea, and infertility in females, and gynaecomastia and impotence in males.

Bromocriptine

A dopamine receptor agonist that serves as a first-line pharmacological treatment for hyperprolactinemia and prolactinomas by suppressing prolactin secretion.

Gynaecomastia

Enlargement of male breast tissue that can occur in conditions of Growth Hormone hypersecretion or hyperprolactinemia due to the structural homology between GH and Prolactin.