Adenyl cyclase activity in human thyroid plasma membranes from normal human thyroid tissue and thyroid adenomas.

The adenylcyclase (AC) activity of crude human thyroid plasma membranes were studied in some detail and conditions for optimal cyclic AMP-production established. Membranes from eight "cold" and two "hot" thyroid adenomas were investigated and compared to membranes from corresponding normal, paranodular tissues. The investigated membranes were found to contain similar basal AC activities, which were stimulated three to five times with TSH and 20--30 times with fluoride. Further, no difference in the TSH-sensitivity of AC from normal and "cold" adenomas could be detected. Thyrotrophin 0.02 mU/ml caused a measurable and 0.15 mU/ml a half-maximal stimulation of the cAMP-production. The data indicate, that disturbances of thyroid hormone production characteristic of thyroid adenomas, are not caused by alterations of the TSH-AC system and suggest that in a thyroid cell the degree of thyroid hormone synthesis do not alter the amount of plasma membrane-bound adenylcyclase.