What Value is there in Assessing Postmenopausal Women for Vitamin D Deficiency?

Abstract

Rev Bras Ginecol Obstet 2017;39:585-586. Vitamin D is included, along with thyroid and steroid hormones, within the unique category of endocrine molecules that act through nuclear receptors. Differently from its partners, until recently vitamin D was thought to be a specialized hormone with an action limited to the control of mineral and bone metabolism. 1 The misconception has been recently reviewed after the recognition that the vitamin D receptor (VDR) as well as the cell machinery to synthesize the active hormone 1,25(OH) 2 D are largely distributed among most tissues and cells. Therefore, vitamin D can potentially modulate an ample diversity of systems and functions, including the cardiovascular system, energy metabolism, immune modulation and cell proliferation. 2 The new knowledge reinvigorated the interest to unveil the ideal levels of vitamin D to obtain osteomineral, as well as non-mineral health.The biochemical measurement of 25-hydroxivitamin D (25-OHD) is considered the best surrogate parameter to assess the status of vitamin D sufficiency. Until 2010, the cut-off point for 25-OHD serum levels was set at 15 ng/mL, and it was an uncommon laboratory parameter, seldom requested by a specialist. Since then, a passionate discussion emerged regarding one key point: what are the ideal serum levels of 25-OHD? Some authors have stated that they are the serum levels that are able to promote the intestinal absorption of calcium, stabilize parathyroid (PTH) serum levels and enable porper bone mineralization. However, this point is still a conundrum.In a perfect world, the new knowledge would stimulate clinical investigation through long prospective studies, as well as randomized double-blinded studies to establish the ideal levels of vitamin D. Conversely, a new proposal was made based on previously published studies, most small and observational investigations, and the ideal serum levels of 25-OHD were set at 30 ng/mL. 3 Curiously, most healthy individuals (70%), independently of age, sex and country, do not have 25-OHD serum levels above 30 ng/mL. A different position was held by the Institute of Medicine (IOM), 4 which estimated that 20 ng/mL were the appropriate levels. The passionate debate about vitamin D deficiency went beyond the realm of science and migrated to the lay media, and patients are currently pressuring physicians to know their vitamin D status, with the hope of preventing diseases simply by taking vitamin D supplementation. 5 The discussion about the appropriate levels of vitamin D goes beyond the focus of the present editorial. Recently published and ongoing well-designed studies aiming at evaluating the effect of vitamin D supplementation on the prevention of diseases will give appropriate scientific support to the query about the role of vitamin D on health maintenance. For instance, in a recent study, vitamin D supplementation (3,750 IU versus 600 IU/day during 1 year) did not ameliorate insulin resistance in overweight individuals. 6 Moreover, The Vitamin D Assessment Study, a random...