Does Birth Control Affect Your Thyroid?

Some hormonal birth control—especially methods containing estrogen—can change thyroid-hormone binding and certain thyroid blood-test results. It does not usually change how much hormone a healthy thyroid produces. Estrogen-containing pills increase thyroid-binding globulin (TBG) levels by up to 50%, which can alter thyroid hormone transport in blood. This doesn't necessarily change actual thyroid hormone production but may affect blood test results. People taking thyroid hormone may need follow-up blood tests after starting or stopping estrogen-containing birth control because their thyroid-hormone dose requirements can change. Fatigue and weight changes can have many causes and do not necessarily indicate a thyroid problem. If these symptoms are persistent or concerning, discuss them with a healthcare professional. If you have thyroid disease, discuss contraceptive options with your healthcare provider to ensure optimal hormone balance and monitoring.