The aetiology and pathogenesis of hyperthyroidism.

Studies of thyroid stimulating activity of serum from thyrotoxic patients has revealed an abnormal prolonged response in the mouse present in 40-60% of patients depending on the criteria used. This agent designated long acting thyroid stimulator (LATS) is a 7S globulin. Transplacental passage of LATS accounts for neonatal thyrotoxicosis-a self-limited disease. LATS is also more readily detected in patients with large goitre, exophthalmos, pretibial myxoedema and recurrence following therapy. Thyroid ablation is usually followed by a fall in the level of LATS. A fall may also be produced by steroid therapy or immunosuppressive agents. LATS probably arises from lymphoid tissue which accounts for the non-suppressibility of the hypersecreting thyroid. Its discovery provides strong evidence that hyperthyroidism is often, though not always, a disorder of immunological tolerance.