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The long-acting thyroid stimulator (LATS) has been thought to be responsible for the hyperthyroidism of Graves's disease. It is detected by its effect on the mouse thyroid gland but cannot be found in all patients with hyperthyroidism. In an attempt to clarify the problem of LATS-negative hyperthyroidism, serum was obtained from untreated patients and its effect in vitro on human thyroid tissue examined, using the activation of adenyl cyclase as a measure of stimulation. Human thyroid adenyl cyclase was activated by both thyroid-stimulating hormone (TSH) and LATS. Thyroid tissue obtained from patients with Graves's disease was relatively less responsive to LATS than was non-toxic thyroid tissue. Of the 24 samples studied five contained LATS and all of these activated adenyl cyclase. The presence of LATS protector in LATS-negative hyperthyroid patients was confirmed but LATS-negative sera had no effect on human thyroid adenyl cyclase activity.

Hashimoto's thyroiditis, autoimmune adrenalitis, pernicious anaemia, and diabetes mellitus are all recognised associations with Down's syndrome. In addition chronic active hepatitis (CAH) resulting from chronic hepatitis B antigenaemia is known to occur in these patients, but an association of autoimmune CAH and Down's syndrome has not previously been described. We report a case in which Down's syndrome was associated with autoimmune CAH, Hashimoto's thyroiditis, and alopecia areata.