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Endocrine Abstracts (2013) 32 P132 | DOI: 10.1530/endoabs.32.P132

1Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy; 2Laboratory of Clinical Chemistry, University Hospital of Pisa, Pisa, Italy.

Primary hyperparathyroidism (PHPT) is defined by hypercalcemia and high PTH levels. In recent years a variant of PHPT has been described, namely normocalcemic PHPT (NPHPT), which is characterized by normal serum calcium and high PTH levels, in the absence of other causes of secondary hyperparathyroidism. The epidemiology of NPHPT is poorly understood. We performed a survey in the early fall in a small Southern Italian village, in which all adult residents (n=1811) were invited to participate. A total of 1056 accepted to participate and blood samples were collected for measurement of serum calcium, albumin, creatinine, PTH and 25OHD. Daily calcium intake was also evaluated using a self-administered questionnaire. A complete set of results was available in 679 subjects (age 18–89 years; 422 F and 257 M). Four women (0.6%) had PHPT. Two hundred and eighty-eight individuals (42.4%) had high PTH (nl: 10–65 pg/ml) and normal albumin-adjusted serum calcium (alb-Ca; nl: 8.6–10.2 mg/dl). Two hundred and sixty-three of them were excluded because of serum 25OHD <30 ng/ml (n=241, 83.7%) or eGFR <60 ml/min per 1.73 m2 (n=22, 7.6%). NPHPT was identified in the remaining 25 subjects (11 F (mean age 47 years, 5 postmenopausal) and 14 M (mean age 47 years), with an overall prevalence of 25/679 (3.5%). PTH, alb-Ca and 25OHD (mean±S.D.) concentrations were 89.0±21.5 pg/ml, 9.0±0.3 mg/dl, and 37.6±7.2 ng/ml, respectively. No relationship was found between PTH and quartile of daily calcium intake. In conclusion, the association of high PTH and normal alb-Ca is rather a common finding, and in the majority of cases is linked to low 25OHD levels and less frequently to renal failure. However, a definite proportion of subjects (3.5%) met the criteria of NPHPT. Longitudinal studies in the latter subjects is needed to establish whether NPHPT represents an early stage of classical PHPT or a separate entity.

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