Barbara Obermayer-Pietsch

Vitamin D and fertility-a systematic review

BACKGROUND Vitamin D has been well-known for its function in maintaining calcium and phosphorus homeostasis and promoting bone mineralization. There is some evidence that in addition to sex steroid hormones, the classic regulators of human reproduction, vitamin D also modulates reproductive processes in women and men. AIM The aim of this review was to assess the studies that evaluated the relationship between vitamin D and fertility in women and men as well as in animals. METHODS We performed a systematic literature search in Pubmed for relevant English language publications published until October 2011. RESULTS AND DISCUSSION The vitamin D receptor (VDR) and vitamin D metabolizing enzymes are found in reproductive tissues of women and men. Vdr knockout mice have significant gonadal insufficiency, decreased sperm count and motility, and histological abnormalities of testis, ovary and uterus. Moreover, we present evidence that vitamin D is involved in female reproduction including IVF outcome (clinical pregnancy rates) and polycystic ovary syndrome (PCOS). In PCOS women, low 25-hydroxyvitamin D (25(OH)D) levels are associated with obesity, metabolic, and endocrine disturbances and vitamin D supplementation might improve menstrual frequency and metabolic disturbances in those women. Moreover, vitamin D might influence steroidogenesis of sex hormones (estradiol and progesterone) in healthy women and high 25(OH)D levels might be associated with endometriosis. In men, vitamin D is positively associated with semen quality and androgen status. Moreover, vitamin D treatment might increase testosterone levels. Testiculopathic men show low CYP21R expression, low 25(OH)D levels, and osteoporosis despite normal testosterone levels.

MECHANISMS IN ENDOCRINOLOGY: The endocrine role of the skeleton: background and clinical evidence

Based on the observation that diabetes, obesity, and hypogonadism influence bone metabolism, the existence of a feedback loop and a common regulation was postulated and an endocrine role ascribed to the skeleton. In the first part of this review, two pathways are described whereby adipose tissue acts on bone mass. In the first, leptin activates the sympathetic nervous system via serotonin and diminishes bone mass accrual. The second pathway functions via the activation of CART (CARTPT) and inhibits bone resorption. The first pathway leads to a decrease in bioactivity of the osteoblast-produced hormone osteocalcin (OC) (part 2). In its undercarboxylated form, OC acts on the three targets pancreas, adipose tissue, and gonads (part 3) and thereby causes an increase in insulin secretion and sensitivity, β-cell proliferation, and male fertility. Insulin (part 4) is part of a recently discovered regulatory feedback loop between pancreas and osteoblasts. It is a strong counterplayer of leptin as it causes a decrease in OPG expression and enhances bone resorption and OC decarboxylation. Numerous clinical studies (part 5) have shown associations of total and undercarboxylated OC and markers of energy metabolism. Interventional studies, to date only performed in murine models, have shown positive effects of OC administration on energy metabolism. Whether bone tissue has an even further-reaching endocrine role remains to be elucidated.

Influence of a positive family history of both type 2 diabetes and PCOS on metabolic and endocrine parameters in a large cohort of PCOS women

OBJECTIVE There is evidence suggesting a strong genetic background of polycystic ovary syndrome (PCOS). We aim to study the metabolic and endocrine characteristics of PCOS women with and without a family history (FHx) of type 2 diabetes mellitus (T2DM) and PCOS. DESIGN Cross-sectional study. METHODS We analysed the association of T2DM FHx and PCOS FHx with metabolic and endocrine parameters in 714 PCOS women. RESULTS A positive FHx of T2DM and PCOS were prevalent in 36.8 and 21.4% of PCOS women respectively. We found an independent association of T2DM FHx with central fat accumulation, obesity, prediabetes, metabolic syndrome (MS), insulin resistance, low HDL and elevated blood pressure (P<0.05 for all). PCOS FHx was independently associated with prediabetes (P<0.05). We observed an independent association of PCOS FHx with clinical and biochemical hyperandrogenism (P<0.05 for all), whereas there was no independent association of T2DM FHx with hyperandrogenism. PCOS women with a positive FHx of both T2DM and PCOS had an adverse metabolic and endocrine profile including a linear increase in risk of obesity, central fat accumulation, MS, prediabetes and low HDL (P<0.05 for all). CONCLUSIONS Our findings suggest that the assessment of FHx might allow risk stratification of PCOS women, which is important considering the high prevalence of PCOS.