Why does starting birth control (contraception) reduce libido (sex drive)?

Why Birth Control Reduces Libido

Birth control pills can reduce libido due to hormonal changes that affect testosterone levels, increase sex hormone binding globulin (SHBG), and alter genital vascularization. These physiological changes directly impact sexual desire and function in many women.

Hormonal Mechanisms

• Combined hormonal contraceptives decrease free testosterone levels and increase sex hormone binding globulin (SHBG), which binds to testosterone and reduces its bioavailability for sexual function 1, 2
• The reduction in free testosterone is measured by the Free Androgen Index (FAI), which decreases significantly in women using hormonal contraceptives 3
• Estrogen components in birth control pills stimulate SHBG synthesis in the liver, further reducing free testosterone availability 4

Vascular and Physical Changes

• Hormonal contraceptives cause measurable changes to genital tissues and blood flow:
  • Decreased clitoral volume 3
  • Increased pulsatility index (PI) of dorsal clitoral arteries, indicating reduced blood flow 3, 5
  • Reduced labia minora thickness and vaginal introitus area 5
• These vascular changes may contribute to:
  • Decreased vaginal lubrication 1
  • Increased pain during intercourse (dyspareunia) 3, 5

Documented Sexual Function Changes

• Studies using validated sexual function questionnaires show:
  • Significant decrease in overall sexual function scores after starting hormonal contraceptives 3, 5
  • Reduced frequency of sexual intercourse 3, 5
  • Decreased frequency of orgasm during intercourse 3, 5
  • Increased pain during intercourse 3, 5

Differences Between Contraceptive Methods

• Combined oral contraceptives (COCs) appear to have more pronounced negative effects on sexual function than other delivery methods 3
• Vaginal ring users reported better vaginal wetness compared to pill users, though both groups experienced decreased sexual desire 3
• Progesterone-only methods can also decrease libido and cause vaginal dryness in some women, but generally to a lesser extent than combined methods 1
• IUDs typically have no significant effect on libido 1

Clinical Considerations

• Sexual dysfunction is a common but underreported side effect of hormonal contraception 1
• The impact on sexual function should be discussed with patients before initiating contraceptive methods 1
• For women experiencing significant libido reduction:
  • Changing to a different contraceptive formulation may help restore sexual function 6
  • Some studies suggest short-term treatment with testosterone-containing preparations can help restore libido in affected women 6
  • Non-hormonal methods like copper IUDs may be preferable for women experiencing severe sexual side effects 1

Common Pitfalls and Caveats

• Sexual dysfunction has multiple potential causes beyond contraception, including:
  • Psychological factors
  • Relationship issues
  • Medication effects (e.g., antidepressants)
  • Underlying medical conditions 4
• Clinicians should not assume that all sexual problems in contraceptive users are method-related
• The freedom from pregnancy anxiety provided by contraception may positively impact sexual function for some women, potentially offsetting hormonal effects 1
• Individual responses to hormonal contraceptives vary significantly, with some women experiencing no change or even improved sexual function 1