Causes of hyperthyroidism in pregnancy

Early pregnancy hormones can temporarily stimulate the thyroid, particularly when nausea and vomiting are severe or when pregnancy hormone levels are high. This form often settles as pregnancy progresses. Graves' disease is an immune condition in which antibodies stimulate the thyroid and may continue during pregnancy or after birth. Thyroid inflammation can release stored hormone, while a thyroid nodule can make hormone independently. Symptoms such as palpitations, excessive sweating, heat intolerance, feeling anxious, difficulty sleeping, or diarrhoea can occur with hyperthyroidism, but pregnancy itself can cause some similar changes. Symptoms alone cannot identify the cause.

A clinician interprets thyroid blood tests alongside the stage of pregnancy, symptoms, examination, and sometimes antibody testing or ultrasound. Untreated or poorly controlled hyperthyroidism can affect the pregnant person and pregnancy, so timely review matters.

Tell your maternity team or doctor about symptoms, a previous thyroid diagnosis, autoimmune illness, thyroid surgery, or medicines. They may repeat thyroid tests and check antibodies to distinguish pregnancy-related changes from Graves' disease. If medicine is needed, the choice and dose are tailored to pregnancy and reviewed regularly; do not start, stop, or change thyroid medicine without advice. Seek guidance before taking iodine-containing supplements or non-prescribed products.

Get urgent medical help for a racing or irregular heartbeat with chest pain, severe breathlessness, fainting, marked agitation, confusion, or a very high temperature. Contact your maternity team promptly if palpitations, vomiting, dehydration, or worsening symptoms make it difficult to eat, drink, rest, or take prescribed medicine.

Ask which thyroid tests are needed, whether pregnancy-related hormone changes or Graves' disease is more likely, how often results should be checked, what symptoms require urgent help, and how treatment will be coordinated with antenatal care.