Endocrinology: Growth Hormone, Thyroid Hormone, and Calcium Homeostasis - VOCABULARY Flashcards

Vocabulary flashcards covering Growth Hormone biology, thyroid regulation, and calcium homeostasis as described in the notes.

Growth Hormone (GH) / Somatotropin

Growth-promoting peptide hormone essential for organismal growth; drives cell proliferation; after adult size is reached, GH promotes protein synthesis via amino acid uptake and fuel availability.

Somatotrophs

GH-secreting cells in the anterior pituitary.

GHRH

Hypothalamic releasing hormone that stimulates GH release from somatotropes.

GHIH (somatostatin)

Hypothalamic hormone that inhibits GH release.

IGF-1

Insulin-like growth factor 1 produced by the liver; mediates many GH effects and promotes growth.

Negative feedback (GH/IGF-1)

GH and IGF-1 inhibit further GH release from the hypothalamus and pituitary.

Lipolysis

Breakdown of fat in adipose tissue to release fatty acids for growth-related fuel.

Glycogenolysis

Glycogen breakdown in the liver to glucose to fuel growth.

Acromegaly

Excess GH after puberty; thickening of bones and soft tissues, especially in the face and hands.

Gigantism

Excess GH before puberty; disproportionate long bone growth.

Dwarfism

Severely short stature due to growth hormone deficiency.

Laron syndrome

GH resistance due to IGF-1 receptor mutations; high GH with low IGF-1 activity.

Pituitary adenoma (somatotrope tumor)

Tumor of GH-secreting pituitary cells causing abnormal GH release.

Growth plate closure

Epiphyseal plates fuse after pubertal sex steroid exposure, ending linear bone growth.

GH resistance

Condition where GH signaling is impaired (e.g., GH or IGF-1 receptor mutations) leading to reduced growth despite high GH.

Thyroid hormone (TH)

T3 and T4; regulate basal metabolic rate and body temperature; produced by thyroid follicles.

TRH

Hypothalamic releasing hormone that stimulates TSH release from the anterior pituitary.

TSH

Thyroid-stimulating hormone from the pituitary; stimulates thyroid follicular cells to secrete T3/T4.

T3

Triiodothyronine; active thyroid hormone with high potency in regulating metabolism.

T4

Thyroxine; prohormone converted to T3 in tissues.

Graves’ disease

Autoimmune stimulation of the TSH receptor causing hyperthyroidism; low TSH and possible exophthalmos.

Hashimoto’s thyroiditis

Autoimmune destruction of thyroid leading to hypothyroidism; often with goiter and high TSH.

Goiter

Enlarged thyroid gland; common in hypothyroid states or Graves’ disease.

Thyroid nodules

Hypersecretory thyroid nodules or cancer causing altered T3/T4 production.

Pituitary thyrotrope tumor

Tumor of thyrotropes; can disrupt TSH production and thyroid hormone levels.

Exophthalmos

Protruding eyes commonly seen in Graves’ disease.

Hypothalamic–pituitary–thyroid (HPT) axis

Regulatory axis: TRH from hypothalamus → TSH from pituitary → T3/T4 from thyroid; negative feedback by T3/T4.

Thyroglobulin

Protein stored in thyroid follicles; precursor to active T3 and T4.

Iodination of tyrosine

Addition of iodine to tyrosine residues on thyroglobulin to form T3 and T4.

Calcitonin

Thyroid C-cell hormone that lowers blood Ca2+ by inhibiting osteoclasts and stimulating osteoblasts.

Parathyroid hormone (PTH)

Parathyroid hormone that raises blood Ca2+ by increasing bone resorption, increasing renal Ca2+ reabsorption, and promoting calcitriol production.

Calcitriol (active vitamin D)

Active form of vitamin D; increases intestinal Ca2+ absorption and works with PTH to regulate Ca2+.

Osteoblasts

Bone-building cells; stimulated by calcitonin and inhibited by PTH; contribute to bone formation.

Osteoclasts

Bone-resorbing cells; stimulated by PTH to release Ca2+ into blood; inhibited by calcitonin.

Calcium homeostasis

Maintenance of blood Ca2+ via PTH, calcitonin, and calcitriol to support heart, bone, and neural function.

Calcium-sensing hormones pathway (PTH, calcitonin, calcitriol)

coordinated hormonal network that maintains extracellular Ca2+ levels.

Calcitriol’s intestinal action

Stimulates intestinal absorption of Ca2+ from the diet.