Birth control is a standard medical treatment for hirsutism, which is the growth of coarse, dark hair in a male-like pattern on a woman’s body. The therapy directly addresses the hormonal imbalance that drives the excessive hair growth. Combined oral contraceptives (OCs), containing both estrogen and progestin, are frequently the first-line medication recommended for women who do not wish to become pregnant. This treatment targets the underlying cause of the hair growth rather than just providing temporary hair removal.
Defining Hirsutism and Hormonal Causes
Hirsutism is defined as the presence of thick, dark, terminal hair in androgen-sensitive areas, such as the upper lip, chin, chest, back, and abdomen. This growth pattern is distinct from the fine, light vellus hair that covers most of the body. The condition affects approximately 5% to 10% of women and is primarily a cosmetic concern, though it can cause psychological distress.
The root cause is almost always an excess of androgens (hyperandrogenism) or a heightened sensitivity of hair follicles to these hormones. Androgens, like testosterone, are naturally produced by the ovaries and adrenal glands. Elevated androgen levels convert fine vellus hair into terminal hair. Polycystic Ovary Syndrome (PCOS) is the most common underlying condition, accounting for the majority of cases, as it causes the ovaries to produce excessive androgens.
How Oral Contraceptives Reduce Androgen Levels
Combined oral contraceptives (OCs) reduce circulating androgens through a dual mechanism. The first mechanism involves the synthetic hormones suppressing ovarian androgen production. The estrogen and progestin components inhibit the release of luteinizing hormone (LH), which signals the ovaries to produce androgens.
The second mechanism is the increase in Sex Hormone-Binding Globulin (SHBG) stimulated by the pill’s estrogen component. SHBG is a liver protein that binds tightly to androgens, particularly testosterone, making them inactive. By raising SHBG levels, the pill effectively reduces free, biologically active testosterone in the bloodstream, often by approximately 50%. This reduction prevents hormonal stimulation of hair follicles, leading to decreased hair growth.
Specific Hormonal Regimens and Adjunctive Therapies
Combined oral contraceptives are the preferred initial pharmacological treatment for hirsutism in women who need contraception, as they address the hormonal cause while also providing menstrual cycle control. Most low-dose OCs are considered equally effective, but some formulations are favored due to the anti-androgenic properties of their progestin components. Progestins like drospirenone or cyproterone acetate, where available, can directly block androgen receptors on the hair follicle itself.
If OCs alone do not achieve satisfactory hair reduction, an anti-androgen medication is often added after several months of initial therapy. Spironolactone is the most common adjunct therapy, typically dosed at 100 mg to 200 mg daily. This medication works primarily by blocking the androgen receptors in the hair follicles, preventing testosterone from having its effect at the tissue level. The combination of an OC and spironolactone is highly effective, with the OC also providing reliable contraception, which is necessary because anti-androgens like spironolactone can cause birth defects if taken during pregnancy.
Realistic Expectations for Hair Reduction
Hormonal treatment for hirsutism is a slow process due to the long hair growth cycle, particularly for terminal hair. A visible reduction in hair density and thickness takes time to manifest. Most women begin to see noticeable improvement only after a minimum of six months of consistent hormonal therapy.
The full effect, which can lead to a 20% to 40% reduction in the hirsutism score, is often not reached until nine to twelve months of continuous use. Hormonal therapy works by preventing the growth of new, coarse hair and reducing the diameter of existing hair.
Since hormonal treatment does not remove terminal hair that has already grown, cosmetic methods like shaving, waxing, or depilatory creams must be used concurrently. For definitive removal of existing hair, patients often rely on permanent methods such as electrolysis or laser hair removal, which can be safely combined with hormonal treatment.