What Is 1st generation progestins

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Last updated: April 15, 2026

Quick Answer: First-generation progestins, developed in the 1950s, include norethindrone and norethynodrel and were the first synthetic compounds used in oral contraceptives. These hormones mimic progesterone and helped launch the birth control pill revolution in 1960 with the FDA approval of Enovid.

Key Facts

Norethindrone, introduced in 1957, was the first widely used first-generation progestin.
Enovid, approved in 1960, was the first oral contraceptive and contained a first-generation progestin.
First-generation progestins are derived from 19-nortestosterone, altering testosterone's structure.
They carry a higher risk of thromboembolic events compared to later generations.
These progestins have strong androgenic activity, leading to side effects like acne and weight gain.

Overview

First-generation progestins were the pioneering synthetic hormones developed in the 1950s to regulate fertility and menstrual cycles. These compounds marked a turning point in reproductive health, enabling the creation of the first effective oral contraceptives.

Derived from modifications of testosterone, specifically 19-nortestosterone, these early progestins mimicked the actions of natural progesterone. Their development laid the foundation for hormonal birth control and expanded treatment options for gynecological disorders.

Norethindrone: First synthesized in 1951 by Frank Colton, it became a cornerstone of early birth control pills and was FDA-approved in 1960.
Norethynodrel: Used in Enovid—the first oral contraceptive—this compound was approved in 1960 and marked a societal shift in family planning.
Chemical structure: These progestins lack the methyl group at carbon-19, differentiating them from testosterone and enhancing progestogenic activity.
Androgenic effects: First-generation progestins exhibit moderate to high androgenic activity, contributing to side effects such as acne, hirsutism, and lipid profile changes.
Metabolic impact: They may reduce HDL cholesterol by 10–15%, increasing cardiovascular risk compared to newer agents.

How It Works

First-generation progestins function by binding to progesterone receptors in the body, suppressing ovulation and altering cervical mucus to prevent sperm penetration. Their hormonal actions also stabilize the endometrium, reducing menstrual bleeding and preventing pregnancy.

Ovulation suppression: By mimicking progesterone, these compounds inhibit the LH surge from the pituitary, preventing follicular rupture in over 95% of cycles.
Cervical mucus thickening: Progestins increase mucus viscosity, creating a barrier that reduces sperm motility and viability within hours of administration.
Endometrial thinning: Continuous exposure leads to atrophic changes in the uterine lining, making it inhospitable to embryo implantation.
Half-life: Norethindrone has a plasma half-life of 8–12 hours, necessitating daily dosing for contraceptive efficacy.
Metabolism: Primarily processed in the liver via cytochrome P450 enzymes, leading to potential interactions with other hepatically metabolized drugs.
Receptor affinity: These progestins have moderate affinity for progesterone receptors but also bind androgen and glucocorticoid receptors, contributing to side effects.

Comparison at a Glance

The following table compares key features of first-generation progestins with later generations:

Feature	1st Gen	2nd Gen	3rd Gen	4th Gen
Introduced	1957	1970s	1980s	1990s
Example	Norethindrone	Levonorgestrel	Desogestrel	Drospirenone
Androgenic Activity	High	Moderate	Low	Very Low
HDL Impact	↓ 10–15%	↓ 5–10%	Neutral	↑ Slight
Thrombosis Risk	↑ 3–4x baseline	↑ 2–3x	↑ 2–3x	↑ 2–3x

While later generations were designed to reduce androgenic side effects and improve lipid profiles, first-generation progestins remain in use due to their proven efficacy and low cost. Levonorgestrel, though second-gen, shares structural similarities and higher androgenic effects, showing a transitional phase in development.

Why It Matters

Understanding first-generation progestins is essential for appreciating the evolution of hormonal therapy and reproductive medicine. These compounds not only revolutionized contraception but also influenced the treatment of endometriosis, abnormal uterine bleeding, and menopausal symptoms.

Historical impact: The 1960 approval of Enovid enabled widespread access to birth control, contributing to the sexual revolution and women’s autonomy.
Clinical use: Norethindrone is still prescribed today for endometriosis, often at 5–10 mg daily, demonstrating long-term utility.
Cost-effectiveness: First-gen progestins are often generic and cost under $10 per month, increasing accessibility in low-resource settings.
Safety profile: Despite higher thrombosis risk, they are considered safe for non-smoking, healthy women under age 35.
Research foundation: These progestins paved the way for over 20 synthetic variants used in modern medicine.
Educational value: Studying them helps medical professionals understand hormonal mechanisms and side effect profiles across generations.

Though newer progestins offer improved safety and tolerability, the legacy of first-generation compounds endures in both clinical practice and medical history.