Hypothyroidism and heart failure: what to know

Low thyroid hormone can slow the heartbeat and affect how strongly the heart pumps. This may contribute to tiredness, reduced exercise tolerance, feeling cold, swelling, or breathlessness. Heart failure can also cause breathlessness, ankle swelling, rapid weight change from fluid, difficulty lying flat, and unusual exhaustion. Because symptoms overlap, they should not be sorted out from symptoms alone.

A clinician may check your pulse and blood pressure, listen to your heart and lungs, review medicines, and use blood tests or heart tests when needed. Having hypothyroidism does not mean that breathlessness or swelling is heart failure.

Book a review if you have new breathlessness, swelling, reduced stamina, or a noticeable change in heartbeat. Bring your medicine list and mention missed thyroid doses, recent dose changes, salt intake, and how symptoms vary through the day. Continue prescribed treatment unless your clinician gives different instructions. Do not use someone else’s diuretics or thyroid medicine.

Seek emergency care for severe or rapidly worsening breathlessness, chest pressure or pain, fainting, blue or grey lips, new confusion, or breathlessness that prevents you from speaking normally. Urgent assessment is also needed for sudden one-sided weakness or a very fast or irregular heartbeat with dizziness. These signs need prompt evaluation regardless of whether hypothyroidism is already known.

Could my thyroid function be affecting my heart symptoms? What tests are appropriate? How should I monitor swelling or breathlessness? Which medicines, fluids, or activities should I avoid?