Presence and influence of cholinergic nerves in the human thyroid

There is evidence that the sympathetic nervous system exerts a control on human thyroid function via an adrenergic innervation of follicle cells. The present study demonstrates that cholinergic nerve fibers also reach follicle cells in the normal human thyroid. In addition, cholinergic agents were found to enhance cGMP accumulation in human thyroid tissue. This effect was blocked by atropine, a muscarinic receptor antagonist, but not by d-tubocurarine, a nicotinic receptor antagonist. These results provide morphological and biochemical arguments supporting a role of the parasympathetic nervous system in the regulation of thyroid function in man.