PurposeTo review the diagnosis and management of thyroid diseases, both metabolic (thyroid storm and myxedema coma) and anatomic (substernal goiter, lymphoma, anaplastic carcinoma) that may require intensive care therapy.Data SourcesEnglish-language articles were identified through a search of the MEDLINE and Index Medicus databases. Bibliographies of retrieved articles were examined for relevant articles.Study SelectionApproximately 250 articles were reviewed. Those articles deemed most representative were utilized. Case reports were included to highlight rare, but potentially lethal complications.Data ExtractionAll data were analyzed by one observer. Limitations of the data are discussed.Data SynthesisGuidelines for determining the etiology of thyrotoxic crisis are outlined. Criteria for distinguishing critically ill hypothyroid patients from those patients with the euthyroid sick syndrome are given. Therapy for both disorders must be aggressive and multifaceted, and detailed management is indicated. Substernal goiter is almost always benign, but may cause various acute complications, including dyspnea, respiratory failure, superior vena caval syndrome, esophageal varices (downhill), and others. Surgery almost always corrects the problem. Lymphomas present with rapid thyroid enlargement. Recent studies suggest that surgery may assume more of a supportive role, used principally to obtain adequate tissue for histologic classification.ConclusionsThyroid disorders can produce emergencies requiring the attention of multiple medical and surgical specialists. While management is often successful, future studies should address the following three areas: a) optimization of thyroid hormone dose for treatment of myxedema coma; b) clarification of the role of radiotherapy and/or chemotherapy for thyroidlymphoma; and c) more effective therapy for anaplastic carcinoma.