Normocalcemic primary hyperparathyroidism: a survey in a southern Italian village

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 234-256-Bone & Calcium Metabolism: Clinical Trials & Case Series
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-240
Claudio Marcocci*1, Edda Vignali1, Antonella Meola2, Roberta Centoni2, Filomena Cetani1, Silvia Chiavistelli2 and Federica Saponaro2
1University of Pisa, Pisa, Italy, 2University of Pisa
Primary hyperparathyroidism (PHPT) is defined by the finding of hypercalcemia and high PTH levels. In recent years a variant of PHPT has been identified, the so-called  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.

To investigate this issue in the early fall of 2010 we performed a survey in a small southern Italian village. All adult residents (n=1811) were invited and 1056 accepted to participate. 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 yr; 422 F and 257 M). Four women (0.6%) had classical PHPT. Two-hundred eighty-eight individuals (42.4%) had high plasma PTH (nl: 10-65 pg/ml) and normal albumin-adjusted serum calcium (alb-Ca; nl: 8.6-10.2 mg/dl). Two-hundred sixty-three of them were excluded because of serum 25OHD <30 ng/ml (n=241, 83.7%) or eGFR <60 ml/min/1.73 m2 (n=22, 7.6%). NPHPT was diagnosed in the remaining 25 subjects [11 F (mean age 47 yr, 5 postmenopausal) and 14 M (mean age 47 yr), with an overall prevalence of 25/679 (3.5%). PTH, alb-Ca and 25OHD (mean ±SD) 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 plasma PTH and quartile of daily calcium intake.

In conclusion, in the present survey the association of high plasma 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 are needed to establish whether NPHPT represents an early stage of classical PHPT or a separate entity.

Nothing to Disclose: CM, EV, AM, RC, FC, SC, FS

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