Infertility is a complex disorder with important medical, psychosocial and economic aspects, affecting about 15% of couples. One of the main causes of female infertility is polycystic ovary syndrome (PCOS). Women with PCOS often suffer from oligo- or anovulation, as well as obesity and insulin resistance. Therefore, PCOS women are considered to be at high risk for metabolic diseases such as type 2 diabetes and the metabolic syndrome as well as for cardiovascular diseases. It is interesting to note that there are cumulative tests that demonstrate an association between the vitamin D status and the pathogenesis, signs and symptoms of PCOS. Ovarian physiology is closely related to the commonly observed metabolic disorders of the syndrome. Furthermore, vitamin D deficiency appears to be related to many of these metabolic characteristics of the PCOS phenotype. Vitamin D status may play an important role in the development of insulin resistance in PCOS, while vitamin D supplementation may improve insulin sensitivity and serum androgen concentrations.
Serum 25(OH)D concentrations were negatively correlated with adiposity markers, including body mass index (BMI) and central obesity. Insulin resistance appears to be related to a severe vitamin D deficiency regardless of the BMI or waist-hip ratio in women with PCOS. Because the insulin receptor gene contains elements sensitive to the vitamin D receptor (VDR), it is plausible that insulin sensitivity can be restored in women with PCOS after treatment with vitamin D. There are studies conducted on humans in this regard. For example, two randomized clinical trials have proved that 4000UI per day of cholecalciferol (precursor D) improve the profiles of blood glucose, HDL cholesterol, LDL and VLDL, insulinemia and insulin resistance in women with PCOS compared to healthy women (Jamilian et al. 2017, Foroozanfard et al., 2017). Another randomized study has virtually confirmed these data, with improvement also of the C reactive protein (PCR), with doses of 50000UI every two weeks (Maktabi et al. 2017).
In a previous study, supplementation with vitamin D also reduced circulating levels of transforming growth factor (TGF-beta), a cytokine that in the context of PCOS induces angiogenesis and ovarian fibrosis (Irani et al. 2015). Some studies have also reported a significant effect of vitamin D supplementation on androgen concentrations: the aforementioned clinical study by Jamilian and co-workers found a significant reduction in testosterone and hirsutism after colecalciferol supplementation. In addition, Asadi and colleagues (2015) sought to understand the effects of vitamin D supplementation on the success rate of intrauterine insemination in 110 infertile women with PCOS (300,000 IU of colecalciferol once vs placebo, 2-month interval between administration of vitamin D and insemination). While there was no treatment effect on pregnancy outcomes, endometrial thickness was significantly higher in vitamin D than in the placebo group.
There are also metanalyses and other investigations that have studied the biological effects of vitamin D in animals and in women with PCOS, in particular on hormonal and biochemical blood and tissue parameters. Overall, the results are in favor of the positive effects of vitamin D in the clinical picture of PCOS, so it is likely that in the immediate future its use in this pathology will become a safe pharmacological reality.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
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