T3 Human Physiology

11, 12, 13, 14, 18, 19, 20

Steroid hormones = smooth ER

Tropic vs Trophic

• Trophic: Refers to hormones that promote growth, size increase, or structural maintenance (hypertrophy or hyperplasia) in target tissues. • Tropic: Refers specifically to hormones that target other endocrine glands to trigger the synthesis and release of another hormone. • The Overlap: Many anterior pituitary hormones are both tropic (stimulating another gland) and trophic (stimulating growth of that gland).

Main Examples and Functions

• Thyroid-Stimulating Hormone (TSH): Both tropic (stimulates the thyroid to release T₃ and T₄) and trophic (increases the size and number of thyroid cells). • Adrenocorticotropic Hormone (ACTH): Stimulates the adrenal cortex to release cortisol and promotes the growth of adrenal cortex cells. • Growth Hormone (GH): Exerts direct trophic and metabolic effects on bones, muscles, and soft tissues. • Prolactin (PRL): Trophic for mammary glands and breast tissue development, though not strictly tropic to another endocrine gland. • Gastrointestinal Trophic Factors: Peptides like gastrin stimulate the mucosal growth of the stomach and small intestine