Regulatory hyperparathyroidism: the role of C-cell hyperplasia.

Four cases with clinical and biochemical evidence of hyperparathyroidism are reported. The syndrome was due to DHT-intoxication of iatrogenic origin in the first case to histologically confirmed C-cell hyperplasia of the thyroid in the three others. The collective term "regulatory hyperparathyroidism" is porposed for the syndromes which, in distinction to secondary parathyroidisms, have a pathogenesis other than a negative calcium balance. Management of the syndrome is discussed with particular emphasis on the removal of the TCT-producing hyperplasia or adenoma, and the restoration of the electrolyte balance.