Oral Contraceptives & HRT

Oral Contraceptives & HRT

1. Definition & scope

• Hormonal contraceptives are hormonal preparations (estrogen ± progestin, or progestin alone) used for reversible suppression of fertility — they separate fertility control from coitus, with ~100% efficacy on perfect use and complete return of fertility on discontinuation (KDT 8e Ch.22, pp.346–9).
• Menopausal hormone therapy (MHT) — historically "HRT" — is estrogen ± progestin given to relieve the perimenopausal syndrome (vasomotor instability, urogenital atrophy) and prevent bone loss; doses are substantially lower than contraceptive doses (G&G 14e Ch.48, pp.982; KDT 8e Ch.22, pp.334).
• The two most common uses of estrogens/progestins are contraception and MHT, but the specific compounds and doses differ substantially between the two settings (G&G 14e Ch.48, pp.959, 982).
• Key potency anchor: 0.625 mg conjugated equine estrogen (CEE) ≈ 5–10 µg ethinylestradiol; MHT uses ~0.625 mg CEE/day whereas combined OCs use 20–35 µg ethinylestradiol/day — so the effective (potency-adjusted) estrogen dose in MHT is lower than in OCs (G&G 14e Ch.48, pp.982).
• Historical milestones: Rock & Pincus (1955) announced successful use of an oral progestin for contraception; addition of a small estrogen enhanced efficacy; Enovid (norethynodrel + mestranol) was the first FDA-approved Pill (1961) (KDT 8e Ch.22, pp.346; G&G 14e Ch.48, pp.976).

A. ESTROGEN & PROGESTIN PHARMACOLOGY (substrate for the rest of the topic)