Endocrine Abstracts

Normocalcemic primary hyperparathyroidism (NPH) is characterized by normal total and ionized serum calcium concentrations and consistently elevated PTH levels. These patients have no obvious causes for secondary elevations of PTH, such as renal disease, vitamin D deficiency or malnutrition. The group consisted of 22 postmenopausal women, six premenopausal women, and two men, aged 58±2 years (range 31–77) investigated between 2011 and 2016.

Results: All subjects had normal renal function and 25-hydroxyvitamin D levels >20 ng/ml (80% had levels >30 ng/ml); none used thiazide diuretics or lithium or demonstrated significant hypercalciuria. The reasons for referral included elevated PTH discovered during the evaluation of low bone mass (n=22), recent fragility fracture (n=2), nephrolithiasis (n=6).

At the time of diagnosis, 70% had osteoporosis by BMD (measured at the lumbar spine, hip or distal one-third of the non-dominant radius), 6.6% had documented fragility fractures, and 20% had nephrolithiasis. PTH was elevated, while albumin-corrected serum calcium, serum phosphorus, alkaline phosphatase activity, and urinary calcium, were all in the mid-normal range.

Nine patients with positive localization studies (cervical ultrasonography, technetium 99 m sestamibi scanning) underwent successful parathyroidectomy, with operative findings of a single adenoma or hyperplasia. Twenty one patients who did not undergo surgery were followed for 3.1±0.3 years (annual serum calcium, PTH and bone mineral density determinations). Hypercalcemia developed in 19% of these individuals. Two of the patients who developed hypercalcemia and three additional patients with persistently normal serum calcium levels underwent successful parathyroidectomy. Fourteen patients were without significant change in serum calcium or development of hypercalcemia, PTH continued to remain elevated.