Precursors: Steroid Hormones and Prostaglandins

Cholesterol & arachidonic acid are the respective precursors of-

Correct Answer: Steroid hormone & prostaglandins

Cholesterol is the precursor of all steroid hormones (and Vitamin D). Arachidonic acid is the precursor of prostaglandins and all eicosanoids.

Cholesterol → Steroid Hormones

• Testosterone (testes, Leydig cells)
• Estrogen (ovary, theca interna of Graafian follicle)
• Progesterone (corpus luteum)
• Cortisol, Aldosterone (adrenal cortex)
• Vitamin D (cholecalciferol) — also from cholesterol

Arachidonic Acid → Eicosanoids

• Prostaglandins (PGE₂, PGF₂α — luteolysis, inflammation)
• Prostacyclin (PGI₂ — vasodilator)
• Thromboxanes (TXA₂ — vasoconstrictor, platelet aggregation)
• Leukotrienes (inflammation, allergy)
• NSAIDs inhibit COX enzyme → block prostaglandin synthesis

Complete Precursor List

• Acetyl-CoA → Cholesterol → Steroid hormones + Vitamin D
• Arachidonic acid → Prostaglandins
• Tyrosine → Thyroxin + Catecholamines (Epinephrine, Norepinephrine)
• Tryptophan → Niacin + Serotonin + Melatonin
• Propionate → Glucose | Hexose → Vitamin C