Hypothyroidism

Hypothyroidism is a common endocrine disorder that mainly affects women and the elderly.

This article outlines the aetiology, clinical features, investigation and management of hypothyroidism.

In the Western world, hypothyroidism is most commonly caused by autoimmune chronic lymphocytic thyroiditis. The initial screening for suspected hypothyroidism is thyroid stimulating hormone (TSH). A thyroid peroxidase antibody assay is the only test required to confirm the diagnosis of autoimmune thyroiditis. Thyroid ultrasonography is only indicated if there is a concern regarding structural thyroid abnormalities. Thyroid radionucleotide scanning has no role in the work-up for hypothyroidism. Treatment is with thyroxine replacement (1.6 μg/kg lean body weight daily). Poor response to treatment may indicate poor compliance, drug interactions or impaired absorption. The significance of elevated TSH associated with thyroid hormones within normal range is controversial; thyroxine replacement may be beneficial in some cases. Unless contraindicated, iodine supplementation should be prescribed routinely in women planning a pregnancy. Where raised TSH levels are detected periconceptually or during pregnancy, specialist involvement should be sought.