Abstract
Study question
Is vitamin D deficiency more prevalent in PCOS patients? Is there a link between vitamin D levels and metabolic status in PCOS subjects?
Summary answer
An inverse relationship between vitamin D levels and metabolic status was demonstrated and it is thought to be responsible of its pathogenesis.
What is known already
PCOS is a multifactorial condition, characterised by failure in oogenesis and anovulation. Obesity is a common condition linked to its clinical features and studies have reported inverse associations between BMI and severity of the condition. Furthermore, 67–85% of PCOS patients have vitamin D deficiency.
Low levels of vitamin D have been found to be closely related to insulin resistance, obesity, or hyperandrogenism and there is a significant association between serum vitamin D levels and reproductive function.
Other factors such as AMH have also been described as possibly involved in the pathophysiology.
Study design, size, duration
We performed a retrospective, analytical and observational study in the Copenhagen Fertility Center. Patients referred with cycle abnormalities, hirsutism, and infertility were evaluated. A total of 778 women were enrolled consecutively from January 2019 to October 2020.
Subjects who had major medical disorders were excluded.
We selected those in which vitamin D was measured in the baseline analysis selecting a total of 396 patients.
The further analysis has been carried out from 100 randomly selected patients.
Participants/materials, setting, methods
Blood samples were drawn after overnight fasting. They were all assayed in the same laboratory.
Biochemical parameters were analyzed using descriptive statistics.
Same parameters were studied after dividing into vitamin D deficiency group or optimal levels using a multiple t-test.
Correlation between variables was determined.
Graphpad Prism program version 8 was used to perform the calculations.
The level of statistical significance was set at P-value < 0.05.
Main results and the role of chance
A total of 100 subjects fulfilling the inclusion criteria were selected randomly from 396 PCOS women.
Serum vitamin D concentrations were highly variable ranging from 16 nmol/L to 175 nmol/L.
The prevalence of vitamin D deficiency was 24% and 41% of the subjects were classified as vitamin D insufficient. Only 35% of our patients had optimal vitamin D values.
We compared data between the group with optimal values of vitamin D (Group A) versus the group with insufficient/deficient vitamin D values (Group B).
We found statistical difference between groups in PTH values, being notably higher in group B compared with group A. Despite no statistically significant difference was obtained, it is important to highlight that the mean of SHBG was lower in group B and the mean of androstenedione, AMH, FAI and HOMA-IR were much higher in this group as well.
Following the HOMA-IR criteria, 55% of patients had insulin resistance. Specifically, 26% had moderate insulin resistance and 29% severe insulin resistance. Levels of vitamin D were negatively correlated with FAI, AMH and HOMA-IR and positively correlated with HDL-Cholesterol and SHBG. Statistically significant differences were evidenced in the correlation between vitamin D and FAI and SHBG.
Limitations, reasons for caution
This is a retrospective observational study on a consecutive admitted patient group with a lack of a control group. Another limitation is the small sample size.
It is difficult to generalize with other degrees of severity. We didn’t assess seasonal variability or if they were taking any vitamin D supplementation.
Wider implications of the findings: Properly randomized clinical trials are mandatory to achieve more conclusive results about the role of vitamin D. Available evidence is promising but not sufficient to draw final conclusions. The aim is to better understand the pathophysiology of the condition and the factors involved and to find new target treatments.
Trial registration number
1
The Relation of Vitamin D Levels to Insulin Resistance and Hepatosteatosis in Obese Children
