Hyperparathyroidism represents as a novel feature of primary
aldosteronism (PA). Its occurrence in patients with the surgically correctable
aldosterone-producing
adenoma (APA) and not in those with bilateral adrenal
hyperplasia suggested that the measurement of
parathyroid hormone could help in differentiating between these subtypes of PA. To test this hypothesis we measured the plasma levels of intact
parathyroid hormone, Ca(2+), and several markers of
calcium/
phosphorus metabolism in 132 hypertensive patients, including 74 with primary (
essential) hypertension and 58 consecutive PA patients. Of the latter, 46 were conclusively diagnosed as APA (by finding of lateralized
aldosterone excess, pathology, correction of the
hyperaldosteronism, and evidence of a fall of blood pressure after
adrenalectomy) and 12 as bilateral adrenal
hyperplasia. Based on these diagnoses we used the area under the receiver operator characteristic curve analysis to assess the accuracy of serum
parathyroid hormone for identifying the PA cases in the whole group and for distinguishing between APA and bilateral adrenal
hyperplasia. In this selected population of hypertensive patients for identifying PA cases, the accuracy of serum
parathyroid hormone tended to be lower than that of the
aldosterone:
renin ratio. However, for discriminating between APA and bilateral adrenal
hyperplasia patients it was better than that under the identity line and also that for the
aldosterone:
renin ratio for pinpointing APA cases among patients with PA. Hence, these findings indicate that raised serum
parathyroid hormone levels are a feature of APA that can be useful for selecting the PA patients to be submitted to adrenal vein sampling.