Effects of oral contraceptives on thyroid function and vice versa

Area of Science:

• Endocrinology
• Pharmacology

Background:

• Thyroid dysfunction is common in women, often coinciding with oral contraceptive (OC) use.
• Limited data exist on how OCs influence thyroid function.

Purpose of the Study:

• To review the interaction between hormonal OCs and hepatic thyroid-binding globulin (TBG) production.
• To examine the effects of OCs on serum thyroxine (T4) and triiodothyronine (T3) levels.
• To assess the impact of OCs on levothyroxine (LT4) treated women and euthyroid women.

Main Methods:

• Literature review focusing on hormonal OCs (estrogen/progesterone-only).
• Analysis of OCs' effects on liver protein synthesis (TBG, SHBG).
• Evaluation of OCs' influence on cardiovascular risk factors in relation to thyroid status.

Main Results:

• Estrogenic components of OCs increase TBG, SHBG, and coagulation factors.
• Progestogens modulate estrogenic effects, potentially reducing androgenic action.
• OCs may increase cardiovascular risk, particularly in women with subclinical hypothyroidism or on LT4 therapy.

Conclusions:

• Hormonal OCs significantly influence thyroid hormone transport proteins.
• Careful consideration of cardiovascular risks is warranted in women using OCs, especially those with thyroid conditions or on LT4.