Pituitary and Thyroid Hormones (Pages 9-13)

Vocabulary flashcards covering key pituitary, hypothalamic, and thyroid topics from the notes.

Hypophysis

The pituitary gland; base of the brain under the hypothalamus; comprises anterior (adenohypophysis) and posterior (neurohypophysis) lobes and coordinates many endocrine functions.

Adenohypophysis

Anterior pituitary; largest lobe; secretes trophic hormones (LH, FSH, TSH, ACTH) and direct effectors (GH, PRL); contains lactotrophs, somatotrophs, thyrotrophs, gonadotrophs, and corticotrophs.

Neurohypophysis

Posterior pituitary; stores and releases oxytocin and vasopressin (ADH) produced in the hypothalamus.

Oxytocin

Hormone from the posterior pituitary; stimulates uterine contractions and milk ejection; also involved in sexual arousal and bonding.

Vasopressin (ADH)

Antidiuretic hormone; regulates water reabsorption in the kidneys via V2 receptors; maintains osmotic balance and blood pressure.

Prolactin (PRL)

Hormone promoting lactation; secreted by lactotrophs; inhibited by dopamine; increases during pregnancy and nursing; acts on breast tissue.

Dopamine (PRL inhibitor)

Hypothalamic neurotransmitter that suppresses prolactin release from the anterior pituitary.

Growth Hormone (GH)

Stimulates growth and metabolism; released from the anterior pituitary; stimulated by GHRH and inhibited by somatostatin; IGF-1 mediates many effects.

IGF-1 (Somatomedin C)

Liver-derived growth factor that mediates GH effects; provides negative feedback to inhibit GH secretion.

Somatostatin

Inhibits GH, TSH, insulin, and several GI hormones; acts as an inhibitory regulator in the hypothalamus and pancreas.

Ghrelin

Hunger hormone produced mainly by gastric cells; stimulates GHRH and GH; increases appetite and influences glucose metabolism; secreted in a pulsatile manner.

GHRH

Growth Hormone Releasing Hormone; stimulates GH release from the anterior pituitary.

GnRH

Gonadotropin-Releasing Hormone; stimulates release of LH and FSH from the anterior pituitary.

LH

Luteinizing Hormone; gonadotropin that triggers ovulation and stimulates sex steroid production.

FSH

Follicle Stimulating Hormone; promotes ovarian follicle development and spermatogenesis.

TSH

Thyroid Stimulating Hormone; stimulates the thyroid to produce T4 and T3.

ACTH

Adrenocorticotropic Hormone; stimulates the adrenal cortex to produce cortisol.

T4 (Thyroxine)

Major thyroid hormone; produced in the thyroid; mostly bound to TBG; converted to T3 in tissues.

T3 (Triiodothyronine)

Active thyroid hormone; largely produced peripherally; more potent than T4.

Free T4 (fT4)

Unbound, biologically active fraction of T4; measured to assess thyroid function.

Free T3 (fT3)

Unbound, active fraction of T3; useful in certain thyroid evaluations.

Reverse T3 (rT3)

Inactive metabolite of T4; increases in non-thyroidal illness; of limited clinical utility.

Thyroglobulin (Tg)

Protein produced by thyroid follicular cells; monitor for recurrence of well-differentiated thyroid carcinoma.

Calcitonin

Secreted by parafollicular C cells; tumor marker for medullary thyroid carcinoma; used post-thyroidectomy monitoring.

TPO Ab

Thyroperoxidase antibodies; autoimmune thyroid destruction seen in Hashimoto thyroiditis and related conditions.

TRAb (TSH receptor antibodies) / TSI

Autoantibodies that stimulate the TSH receptor; central in Graves disease; predict neonatal risk when transplacental.

Graves Disease

Autoimmune hyperthyroidism caused by TSH receptor-stimulating antibodies; goiter and elevated thyroid hormones.

Urinary iodine measurement

Estimate of dietary iodine intake by urinary excretion; reflects recent iodine status.

Iodine

Essential element for thyroid hormone synthesis; intake determined by diet.

Neonatal TSH screening

Newborn screening test measuring TSH to detect congenital hypothyroidism; abnormal levels prompt follow-up testing.

Hashimoto thyroiditis

Autoimmune thyroiditis with anti-TPO antibodies; typically leads to hypothyroidism.

L-thyroxine (Levothyroxine, LT4)

Synthetic T4 used to treat hypothyroidism; taken on an empty stomach at the same time daily; goal TSH 0.5–2.0 mIU/L in primary hypothyroidism.

Recombinant human TSH (rhTSH)

Synthetic TSH used to stimulate thyroid tissue in evaluation for residual or recurrent thyroid cancer.

Medullary thyroid carcinoma (MTC)

Thyroid cancer from C cells; calcitonin is a tumor marker for monitoring.

Transsphenoidal adenomectomy

Surgical removal of a pituitary adenoma via a transsphenoidal approach.

GH Deficiency (GHD)

Limited GH production; in children causes growth failure; in adults causes metabolic and body composition issues.

Acromegaly

GH-secreting pituitary adenoma in adults; causes enlarged hands/face, prognathism, sweating, and metabolic complications.

Gigantism

GH overproduction before epiphyseal closure, leading to excessive linear growth.

Panhypopituitarism

Complete loss of pituitary hormone production; affects multiple endocrine axes.

Monotropic hormone deficiency

Deficiency of a single pituitary-hormone axis.