April - June 2007, Volume 3, Issue 2

Branisteanu DD, Bottermann P, Zbranca E, Mogos V

Sunlight exposure and vitamin D supplementation at the institutionalized elderly - effects on calcium and bone metabolism

Acta Endo (Buc) 2007, 3 (2): 169-178
doi: 10.4183/aeb.2007.169

Aims: we wanted to check the importance of sunlight exposure and vitamin D supplementation in reverting secondary hyperparathyroidism at IIIrd age institutionalized patients.\r\nDesign: cross-sectional study of calcium and bone metabolism in a group of 123 institutionalized IIIrd age volunteers after winter period, followed by a prospective double blind placebo-controlled study of effects upon calcium and bone metabolism, serum 25OHD3, 1,25(OH)2D3 and PTH levels of daily sunlight exposure during the summer months, with or without vitamin D supplementation (2000 IU 25OH-D3 po, daily). The study was performed on volunteers from the Elderly Resting House of Copou,\r\nIasi, Romania. 25OH-D3 was measured by an inhouse RIA technique. 1,25(OH)2D3 was measured by HPLC, serum calcium by photocolorimetry, bone alkaline phosphatase by immunoenzymatic technique, whereas serum PTH and urinary deoxypyridinoline (DPD) were measured by IRMA. Data was compared using Student&#8217;s t test and correlation analysis (R2). Almost all volunteers (93.5%) had low 25OH-D3 values, but normal or even increased levels of the active hormone, 1,25(OH)2D3. High PTH was found in 41 cases (33.3%), of which three were primary hyperparathyroidism, whereas the others had low or low-normal calcium levels (secondary hyperparathyroidism). More than half of the cases had high DPD levels, suggesting high bone turnover. Bone turnover parameters were higher in females than in males (p<0.05). A positive correlation between PTH and urinary DPD was noticed (R2=0.351). We further supplemented the vitamin D intake in 42 volunteers with a daily dose of 2000 IU of 25-OHD3 for three months in the summer period, whereas other 42 volunteers received placebo (vitamin B). Normalization of 25-OHD3 levels was seen in both vitamin D and placebo-treated sun-exposed groups. A more significant increase in 25OHD3, and also of 1,25(OH)2D3 at the upper limit of normal was however observed in the vitamin D-treated group. Normalization of serum PTH, but not of turnover parameters was observed in both groups. Mild hypercalcemia and increase in serum creatinine were noticed in the vitamin D-treated group.\r\nConclusions: Secondary hyperparathyroidism might be of importance in high turnover bone loss at institutionalized IIIrd age patients. Women seem to be more at risk, possibly due to sex hormone depletion. PTH-induced 1&#945; hydroxylation in the elderly with undamaged kidney function partially compensates the paucity of vitamin D substrate, by normalizing active hormone levels. Mild sun exposure at institutionalized patients increases skin resources of vitamin D, normalizing 25OH-D3 levels and reverting secondary hyperparathyroidism. Oral vitamin D supplementation added to sunlight exposure should be done with caution, since it might be accompanied in certain patients by hypercalcemic or nephrotoxic effects at doses higher than 2000 IU/day.

Keywords: vitamin D, senile osteoporosis, hydroxylation, hyperparathyroidism

Correspondence: Dumitru D. Branisteanu, MD, PhD, Clinic of Endocrinology, "St. Spiridon" University Hospital, Independentei Str. 1, Iasi, Romania, Tel. 0232 213 226, Fax 0232 278 224, email dumitru_Branisteanu@yahoo.com