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The secretory response of abnormal parathyroid glands obtained surgically from eleven patients with primary and secondary hyperparathyroidsm was tested in vitro. Short term flask studies were used to measure release of parathyroid hormone (PTH) at high (3.0 mM) and low (0.5 mM) calcium. Of eight adenomas, all but one showed increased release of hormone when exposed to low calcium ("responsive to calcium"), the degree of stimulation at three hours ranging from 15 to 209%. By comparison, two normal human glands were stimulated an average of 180%. Glands from three patients with secondary hyperplasia were also responsive to calcium. Thus, parathyroid glands from patients with primary and secondary hyperparathyroidism were characterized by a spectrum of responsiveness to calcium, and absolute "autonomy" was unusual. Even at high calcium concentrations, hormone release persisted at a low but definite level ("basal secretion"). The total number of functioning parathyroid cells is therefore a principal determinant in the oversecretion of PTH in hyperparathyroidism.
Birnbaumer et al. (Fri,) studied this question.