Hyperthyroidism in pregnancy manifests as a hypermetabolic condition caused by increased production of thyroid hormones. The most common causes of hyperthyroidism in pregnancy are autoimmune thyroid disease, such as Graves’ disease, or a transient increase in hCG levels in early pregnancy known as gestational transient thyrotoxicosis. Less common causes include multinodular goiter, toxic adenoma, functional thyroid cancer metastases, struma ovarii, and thyrotropinoma. Elevated thyroid hormone levels can also be caused by subacute thyroiditis and exogenous hormone intake. Diagnosis is made based on clinical examination and laboratory tests. Assessment of thyroid activity includes measurement of serum concentrations of TSH and thyroid hormones, thyroxine, and triiodothyronine. Thyroid hormones are an important factor for normal fetal growth and development. Early detection and treatment of hyperthyroidism reduces the risk of complications and adverse pregnancy outcomes. Antithyroid drugs, methimazole and propylthiouracil, are the gold standard in the treatment of hyperthyroidism in pregnancy. Decisions on which medication to use are based on gestational age, with consideration of both teratogenicity and side effects. Surgical treatment is considered when there are contraindications to the use of antithyroid drugs and is usually performed in the second trimester. Pregnancy, like breastfeeding, is an absolute contraindication to treatment with radioactive iodine. Treatment and follow-up of patients should be continued in the postpartum period due to the increased risk of developing postpartum hyperthyroidism.