Secretion and adenylate cyclase in thyroid nodules.

Thyrotropin (TSH)- and sodium fluoride (NaF)-sensitive adenylate cyclase (AC) activity was measured in ten cases of "cold" thyroid nodules and compared with perinodular tissue. Findings were correlated with the ultrastructure of the nodular and perinodular tissue. Comparisons of the results of assay studies revealed an increase of basal and NaF- and TSH-stimulated AC activity in cold lesions. There was no dissociation of NaF- and TSH-sensitive AC. Ultrastructural findings disclosed a lack of correlation between elevated AC activity and the expected organelle profile indicative of stimulation. Since organelle modulations that are associated with increased protein synthesis were not observed in the face of increased AC activity, an unknown intracellular defect may exist in the expression of the AC-cyclic AMP (adenosine 3':5'-cyclic phosphate) system in cold thyroid nodules.