MCAT Hormones 2026

TSH

Peptide | Anterior pituitary → thyroid | Stimulates T3/T4 production and release.

ACTH

Peptide | Anterior pituitary → adrenal cortex | Stimulates cortisol release.

FSH

Peptide | Anterior pituitary → gonads | Females: follicle development; males: spermatogenesis.

LH

Peptide | Anterior pituitary → gonads | Females: ovulation; males: stimulates testosterone production.

GH

Peptide | Anterior pituitary → many tissues/liver | Promotes growth, protein synthesis, and IGF-1 production.

Prolactin

Peptide | Anterior pituitary → mammary glands | Stimulates milk production.

Oxytocin

Peptide | Made in hypothalamus, released by posterior pituitary → uterus/breast | Uterine contractions and milk letdown.

ADH

Peptide | Made in hypothalamus, released by posterior pituitary → kidneys | ↑ water reabsorption; helps maintain blood volume/osmolality.

T3

Modified amino acid | Thyroid → most tissues | ↑ metabolic rate; important for growth and development.

T4

Modified amino acid | Thyroid → most tissues | Thyroid hormone; largely converted to T3; ↑ metabolic activity and supports development.

Calcitonin

Peptide | Thyroid C cells → bone/kidney | ↓ blood Ca²⁺.

PTH

Peptide | Parathyroid glands → bone/kidney; indirectly intestine | ↑ blood Ca²⁺.

Thymosin

Peptide | Thymus → developing T cells | Promotes T-cell development, especially during childhood.

Epinephrine

Hormone released by the adrenal medulla that triggers the fight-or-flight response.

Norepinephrine

• Neurotransmitter usually released by sympathetic postganglionic neurons; helps increase alertness and blood pressure.

Cortisol

Steroid | Adrenal cortex → many tissues | Long-term stress response; ↑ blood glucose; ↑ protein catabolism; ↓ inflammation/immune activity.

Aldosterone

Steroid | Adrenal cortex → kidney | ↑ Na⁺ reabsorption; water follows → ↑ blood volume and blood pressure.

Insulin

Peptide | Pancreatic β cells → liver/muscle/adipose | ↓ blood glucose; promotes glucose uptake, glycogen synthesis, and fat storage.

Glucagon

Peptide | Pancreatic α cells → mainly liver | ↑ blood glucose; promotes glycogen breakdown and glucose production.

Somatostatin

Peptide | Pancreatic δ cells → digestive/endocrine tissues | Inhibits many digestive and endocrine processes.

Testosterone

Steroid | Testes → reproductive tissues | Male characteristics; supports spermatogenesis.

Estrogen

Steroid | Ovaries/placenta → reproductive tissues | Female characteristics; promotes endometrial growth.

Progesterone

Steroid | Ovaries/placenta → uterus | Supports endometrium and pregnancy.

ANP

Peptide | Heart atria → kidneys/vessels | ↑ Na⁺ and water excretion → ↓ blood volume and blood pressure.

EPO

Peptide | Kidney → bone marrow | Stimulates RBC production, especially in response to low oxygen.

GnRH

Peptide | Hypothalamus → anterior pituitary | Stimulates FSH and LH release.

Calcitriol

Steroid-like active vitamin D | Kidney → intestine/bone/kidney | ↑ intestinal Ca²⁺ absorption; helps increase blood Ca²⁺.

Renin

Enzyme, not a hormone | Kidney → angiotensinogen | Initiates RAAS → ultimately promotes ↑ blood pressure and blood volume.

Angiotensin

Peptide hormone | RAAS | Angiotensin II causes vasoconstriction, ↑ aldosterone, ↑ Na⁺/water retention → ↑ blood pressure.

Melatonin

Hormone | Pineal gland → brain/body | Helps regulate circadian rhythm and sleep-wake cycles.