Abstract:
One of the most characteristic presenting features of hyperthyroidism is weight loss, despite an increased appetite. This phenomenon is easily understandable, as hyperthyroidism is accompanied by a rise in metabolic rate, energy expenditure and thermogenesis which is clearly not matched by an increased appetite and caloric intake in the vast majority of patients. Consequently a decrease in adipose tissue and muscle results. (Curiously a small proportion of hyperthyroid patients, fewer than 10%, present with weight gain owing to an increased appetite that exceeds the rise in metabolic rate.
Reference:
Ross, I. L., & Levitt, N. S. (2003). Excessive weight gain following therapy for hyperthyroidism-a major problem: editorial. South African Medical Journal, 93(7), p-515.