12.4 Lesson 4: Causes of Hair Loss
Thyroid Causing Hair Loss
- Hair follicles, due to their high degree of metabolic activity, are sensitive to concentrations of thyroid hormones due to the thyroid’s influence on the cellular metabolism of proteins, carbohydrates, lipids and minerals.
- Up to 50% of hypothyroid (under-active thyroid) cases cause hair loss. At first the hair loss is usually limited to the scalp but may “spread” to the eyebrows, chest, arms, and leg hair. Losing the outer one third of eyebrow hair (called Sign of Hertoghe) is a distinctive symptom of 25% of people with hypothyroidism.
- Sometimes the onset of hypothyroidism promotes genetic alopecia as a drop in thyroid hormone production leads to a reduction of Sex Hormone Binding Globulin (SBHG) concentration in the blood. With reduced SBHG levels, more testosterone is available for conversion to dihydrotestosterone.
- Up to 50% of individuals with hyperthyroidism (over-active thyroid) develop scalp hair loss. The extent of hair loss is usually more limited than observed with hypothyroidism. Remaining hair is often very fine, of poor quality and easily breakable. Sometimes an early symptom of hyperthyroidism is loss of pigment and early gray hair development.
- Hair loss due to either hypo- or hyper- thyroidism is diagnosed with the help of blood tests to identify any change in concentrations of thyroid stimulating hormone (TSH), thyroxine, and other thyroid gland-controlled hormones. If the thyroid problem is rectified with medication, there can be reactivation of hair follicles, improvement in hair quality, and hair regrowth.