The principal types of thyroid disorders described herein can be recognized and evaluated clinically and biochemically by the obstetrician/gynecologist. Most patients with diffuse goiter should be referred for further evaluation and an RAI scan arranged while this consultation is awaited. Patients with solitary thyroid nodules should be referred for FNAB. Primary hypothyroidism without significant goiter can be treated without specialist referral, except in patients at high risk for ischemic coronary disease or arrhythmia. Primary hyperthyroidism, apart from subacute and postpartum thyroiditis, should be referred for specialist evaluation and definitive therapy. An RAI scan and uptake should be ordered, and beta-blocker therapy can be initiated as interim therapy in symptomatic patients. Patients with secondary (i.e., hypothalamic- or pituitary-based) thyroid dysfunction should always be referred for evaluation and treatment of the primary intracranial cause. There are several causes of abnormal thyroid function tests in apparently euthyroid patients, and the clinical context often provides important evidence of their nature. Clinical judgment is an important factor in knowing when to arrange specialist consultation.