A method for treating hypothyroidism by local administration of a neurotoxin, such as a botulinum toxin, to a thyroid, thereby reducing an inhibitory effect upon thyroid hormone secretion. A method for treating hyperthyroidism by local administration of a neurotoxin, such as a botulinum toxin, to a sympathetic ganglion which innervates the thyroid, thereby reducing a stimulatory effect upon thyroid hormone secretion. Methods for treating calcium metabolism disorders by local administration of a neurotoxin to modulate calcitonin secretion are also disclosed.