Hypothyroidism and Alopecia: A Clinical and Pathophysiological Review

Hypothyroidism is a common endocrine disorder that can produce multiple cutaneous and hair abnormalities. Alopecia, or diffuse hair loss, is a recognised manifestation of thyroid hormone deficiency and may be an important clinical clue to underlying thyroid dysfunction. Thyroid hormones influence the hair follicle cycle, cellular proliferation, differentiation, and metabolic activity. In hypothyroidism, alterations in the normal hair cycle may result in increased shedding, dry and brittle hair, reduced hair growth, and diffuse scalp thinning. Alopecia may also result from autoimmune disorders, nutritional deficiencies, medications, and other endocrine conditions, making clinical evaluation important. This review discusses the relationship between hypothyroidism and alopecia, underlying mechanisms, clinical presentation, diagnostic evaluation, and management considerations.