Endocrine Abstracts

Introduction: Vitamin D insufficiency is very common among Spanish adults. It is well established there is an inverse relationship between vitamin D and PTH levels. The diagnostic approach of an increased serum PTH concentration in a normocalcemic normophosphatemic patient is frequent in routine practice and the deficiency of vitamin D is the major cause of secondary hyperparathyroidism (SHPT). The aims of this study were to evaluate the prevalence of SHPT in a cohort of normocalcemic patients with elevated serum PTH levels and deficiency/insufficiency of vitamin D and to analyze the correlation between PTH and vitamin D levels.

Methods: Fifty-one patients with elevated PTH levels and a 25OHD <30 ng/ml were included. All patients were treated with vitamin D for 3–6 months and all parameters were re-evaluated. Patients with diabetes and chronic kidney disease were excluded.

Results: Fifty-one patients were included (60.8% female; 62.24±14.28 median age). Baseline characteristics were: Serum calcium: 9.766±0.84 mg/dl, serum phosphate: 2.81±0.79 mg/dl, calciuria: 84.59±110 mg/dl per 24 h, PTH: 112.28±35 and 25(OH) vitamin D: 16.21±5.3 ng/dl. After treatment with vitamin D there was a significant increase of 25(OH) vitamin D levels (38.47±24, P<0.0001) and a significant decrease of PTH levels (88.02±36.09 P<0.001), serum calcium (9.8±0.6 P<0.037), serum phosphorus (3.11±0.598 P<0.018) and calciuria (119.37±110.12 mg/24 h; P<0.032). Five patients were diagnosed of primary hyperparathyroidism (9.8%) and two patients (3.92%) of normocalcemic primary hyperparathyroidism. Plasma 25(OH)D3 levels correlated negatively with PTH levels (r=−0.465 (P<0.01).

Conclusions: Vitamin D deficiency/insufficiency is the major cause of SHPT. To adequately assess this condition is critical to replenish levels of vitamin D. PTH levels correlate negatively with levels of vitamin D.