Recently, the question of whether vitamin D exerts an effect on the pathogenic process of infertility has become the centre of attention. There are some controversial conclusions on this issue. Based on previous studies, we sought to explore the difference of serum 25-hydroxyvitamin D , 1,25-dihydroxyvitamin D levels between infertile patients and fertile men, and to find the influence on semen quality. The analysis of serum 25-hydroxyvitamin D level showed no significant difference between infertile patients and fertile men. However, the levels of serum 1,25-dihydroxyvitamin D in oligospermia (P < 0.05), asthenospermia (P < 0.01), oligoasthenospermia (P < 0.05) and azoospermia (P < 0.01) patients were significantly lower than those in fertile men. Moreover, serum 1,25-dihydroxyvitamin D level was positively correlated with progressive motility and total sperm number in infertile patients. In addition, a positive correlation between serum prolactin and 1,25-dihydroxyvitamin D was observed in fertile men. Our results indicated that lower vitamin D could be a risk factor for poor semen quality in infertile men. The 1,25-dihydroxyvitamin D , as the biologically active form of vitamin D, may be more significant.

Severe Vitamin D deficiency could be detrimental to early embryonic development and increase the risk of early SPL.

Background: Vitamin D insufficiency and deficiency in childhood are common. However, the status and influential factors of vitamin D during different ages are not clear. This study aimed to survey vitamin D concentrations in children aged 0 to 6 years and explore its influential factors. Methods: A total of 6953 children were recruited in Wuxi City of East China from January to December in 2016. Enzymelinked immunosorbent assay was used to determine the serum concentrations of 25-hydroxyvitamin D [25(OH)D]. Results: The median vitamin D concentrations in the infant group (0-1 years of age) was 69.40 nmol/L, which were higher than that in both the toddlerhood group (1-3 years of age; 62.30 nmol/L) and the preschool group (3-6 years of age; 50.85 nmol/L). In addition, the median vitamin D concentrations were 71.70 nmol/L in summer, which was higher than that in spring (64.25 nmol/L), autumn (62.95 nmol/L) and winter (64.10 nmol/L). However, no difference was observed between genders (P = 0.974). Furthermore, the prevalence of vitamin D deficiency (< 50 nmol/L) was 48.1% in the preschool group (3-6 years of age), which was higher than the 21.2% vitamin D deficiency in the toddlerhood group (1-3 years of age) and the 17.9% vitamin D deficiency in the infant group (0-1 years of age). Interestingly, a nonlinear association between 25(OH) D and air temperature was observed. Conclusions: A high prevalence of vitamin D deficiency was common in a Chinese population of children 0-6 years old, especially in the preschool-aged children. Therefore, we suggested that we should pay more attention to vitamin D supplementation in Chinese young children.