Hypothalamic-Pituitary-Endocrine Axis and Endocrine Pharmacology

A comprehensive set of vocabulary flashcards covering the hypothalamic-pituitary-endocrine axis, including hormone classifications, pharmaceutical analogues, clinical disorders, and treatment modalities.

Endocrinology

The study of the biosynthesis of hormones, their sites of production, and the mechanisms of their action and interaction.

Class 1 Hormones

Hormones that act predominantly via nuclear receptors to modulate transcription in target cells, such as steroid hormones, thyroid hormone, and vitamin D.

Class 2 Hormones

Hormones that typically act via membrane receptors to exert rapid effects on signal transduction pathways, including peptide and amino acid hormones.

Negative Feedback Regulation

A mechanism superimposed on positive feed-forward regulation that permits precise control of hormone levels.

Pro-opiomelanocortin (POMC)-derived hormones

A group of anterior pituitary hormones derived by proteolytic processing that include corticotropin (ACTH) and $\alpha$-MSH.

Somatotropic family of hormones

A group of hormones including Growth Hormone (GH), Prolactin (PRL), and placental lactogen.

Glycoprotein hormones

A family of pituitary hormones consisting of TSH (thyrotropin), LH (lutropin), FSH (follitropin), and hCG.

GHRH (Growth Hormone-Releasing Hormone)

A peptide with $44$ amino acids produced by hypothalamic neurons that stimulates GH secretion.

Ghrelin

A $28$-amino acid peptide synthesized in the fundus of the stomach that stimulates appetite and GH secretion via the GH secretagogue receptor.

Somatostatin (SST)

A hormone synthesized in widely distributed neurons that mediates the negative-feedback action of GH.

Insulin-like Growth Factor 1 (IGF-1)

Also known as somatomedin C, it exerts negative feedback usually through direct effects on the anterior pituitary and by stimulating hypothalamic SST secretion.

Principal form of GH

A single polypeptide chain of $22\,kDa$ that has two disulfide bonds and is not glycosylated.

JAK/STAT cytokine receptor superfamily

The specific cell surface receptors through which Growth Hormone mediates its biological effects.

Recombinant human GH (rhGH)

A preparation administered subcutaneously $6-7$ times per week with active blood levels persisting for approximately $36$ hours.

Dopamine (DA)

The major inhibitory regulator of Prolactin (PRL) secretion, interacting with the D2 receptor on lactotropes.

Gigantism

A clinical syndrome caused by GH excess in patients with unfused epiphyses, resulting in increased longitudinal growth.

Acromegaly

A clinical syndrome resulting from GH excess in adults.

Hyperprolactinemia

An endocrine abnormality causing galactorrhea, amenorrhea, and infertility in women, and loss of libido or erectile dysfunction in men.

Octreotide

An SST analogue that is $100\%$ bioactive with a serum $t_{1/2}$ of about $90\,\text{min}$ and a duration of action of approximately $12\,\text{hrs}$.

Pasireotide

A long-acting cyclohexapeptide SST analogue with high affinity for the SST5 receptor, approved for treating Cushing disease.

Pegvisomant

A GHR antagonist that binds to the Growth Hormone receptor but does not activate JAK-STAT signaling or stimulate IGF-1 secretion.

Bromocriptine

A semisynthetic ergot alkaloid and D2 receptor agonist used to inhibit PRL release and manage Parkinson disease.

Cabergoline

An ergot derivative with a long $t_{1/2}$ of $\sim 65\,\text{h}$; it is the preferred drug for hyperprolactinemia due to higher efficacy and lower adverse effects.

Quinagolide

A nonergot D2 receptor agonist with a $t_{1/2}$ of about $22\,\text{h}$ that should not be used when pregnancy is intended.

Somatropin

The term for GH preparations produced by recombinant DNA technology whose sequences match native GH.

Mecasermin

Recombinant human IGF-1 administered by subcutaneous injection for patients with GH resistance or deficiency.

Tesamorelin

A synthetic N-terminally modified form of human GHRH resistant to dipeptidyl peptidase 4, approved for HIV-associated lipodystrophy.

Menotropins (hMG)

A purified extract of FSH and LH obtained from the urine of postmenopausal women.

Urofollitropin (uFSH)

A purified preparation of human FSH extracted from the urine of postmenopausal women.

Choriogonadotropin alfa (rhCG)

A recombinant form of human chorionic gonadotropin packaged and dosed on the basis of weight.

Ovarian hyper-stimulation syndrome (OHSS)

An adverse effect of gonadotropin therapy associated with ovarian enlargement, ascites, and electrolyte imbalance.

Gonadorelin

An acetate salt of synthetic human GnRH used for stimulation or diagnosis of LH responsiveness.

Endometriosis

The presence of estrogen-sensitive endometrium outside the uterus, which can be treated by continuous GnRH agonist administration.

GnRH Receptor Antagonists

Synthetic decapeptides like Ganirelix and Cetrorelix that competitively inhibit FSH and LH secretion.

Oxytocin

A $9$-amino-acid peptide that stimulates uterine contractions and milk letdown; it has a circulating half-life of $5\,\text{minutes}$.

Atosiban

An antagonist of the oxytocin receptor used as a treatment (tocolysis) for preterm labor.

Vasopressin (Antidiuretic Hormone)

A nonapeptide that activates V1 receptors for vasoconstriction and V2 receptors for water resorption in renal collecting tubules.

Desmopressin

A modified vasopressin analogue with a half-life of $1.5-2.5\,\text{hours}$, used for pituitary diabetes insipidus and hemophilia A.

Conivaptan

A nonpeptide vasopressin antagonist with high affinity for both V1a and V2 receptors.

Tolvaptan

A nonpeptide vasopressin antagonist with a $30$-fold higher affinity for V2 receptors compared to V1 receptors.