Background: The associations between serum vitamin D (VD), serum testosterone (TT) and metabolic syndrome are complex and with limited published research, particularly on the effects of VD treatment on sexual hormones, erectile function and the metabolic syndrome.Objectives: This study assessed whether a monthly high dose VD treatment for 12 months in VD deficient middle-aged men was associated with: changes in levels of sexual hormones, improvement of diabetes control and metabolic syndrome components, better erectile function [International Index of Erectile Function (IIEF)-5 questionnaire]; and changes in a prostate marker.Materials and methods: Descriptive research of a prospective study, conducted between October 2014 and September 2015, 102 male patients 35 [(SD: 53.210.5), (range 35-64)] years with deficient serum VD level (<30ng/mL) were included in the study. Participants were followed up for one year, with monitoring at 3-, 6-, 9- and 12-months. At the initial baseline visit, a complete medical examination was conducted, and blood was drawn for laboratory tests for above biochemical and hormonal variables under examination. Participants received an initial VD (Ergocalciferol; oral solution 600000IU/1.5ml), and followed a VD treatment regime thereafter. At the four follow up visits (3, 6, 9 and 12 months), blood was collected, and patients' erectile function was evaluated by IIEF-5 questionnaire.Main outcome measures: During the follow up visits, all the biochemical and hormonal (TT, estradiol and luteinizing hormones, HbA1c, serum lipids profile) were assessed, and patients' erectile function was evaluated by IIEF-5 questionnaire.Results: Patients' mean age was 53.2 +/- 10.4 years. Serum VD exhibited significant increments (p<0.001) from baseline (15.16 +/- 4.64ng/mL), to 3 (31.90 +/- 15.99ng/mL), 6 (37.23 +/- 12.42ng/mL), 9 (44.88 +/- 14.49ng/mL) and 12 months (48.54 +/- 11.62ng/mL), and there was significant stepladder increases in both serum TT level (12.46 +/- 3.30 to 15.99 +/- 1.84nmol/L) and erectile function scores (13.88 +/- 3.96 to 20.25 +/- 3.24) (p<0.001 for both). We also observed significant stepladder decreases in estradiol (87.90 +/- 27.16 to 69.85 +/- 14.80pmol/L, p=0.001), PTH (from 58.52 +/- 28.99 to 38.33 +/- 19.44pg/mL, p<0.001) and HbA1c levels (7.41 +/- 2.85 to 6.66 +/- 1.67%, p=0.001). Mean BMI significantly decreased from 33.91 +/- 6.67 to 33.14 +/- 6.35kg/m(2) (p=0.001); and PSA values significantly increased from 0.59 +/- 0.30 to 0.82 +/- 0.39ng/mL (p<0.001) at the end of the 12 months' follow-up. There were no changes in LH levels.Conclusion: This study demonstrated that VD treatment improves testosterone levels, metabolic syndrome and erectile function in middle-aged men. More randomized placebo-controlled interventional trials of VD treatment in patients with the metabolic syndrome and low TT could assist in uncovering the putative roles of VD.
