No Association between 25-Hydroxyvitamin D and Insulin Resistance or Thyroid Hormone Concentrations in a Romanian Observational Study

Abstract

Background and objectives: Vitamin D is involved in insulin resistance through genomic and non-genomic mechanisms. Several observational and randomized studies have discrepant results; some of them showed an improved insulin resistance (IR), and others a neutral effect after vitamin D deficiency is corrected. Materials and Methods: We designed a retrospective observational study that included all women who presented for 33 months in an outpatient clinic in Bucharest, Romania. Results: We analyzed 353 patients with a mean age of 58.5 ± 13.7 years, a mean body mass index (BMI) of 27.36 ± 4.87 kg/m−2, and a mean level of 25-hydroxyvitamin D (25OHD) of 39.53 ± 15.73 ng/mL. There were no differences in the calculated Homeostatic Model Assessment of Insulin Resistance variants 1 and 2 (HOMA-IR) and the Quantitative Insulin Sensitivity Check Index (QUICKI) between women with vitamin D deficit versus normal values. In multivariate analysis, there was no significant relation between 25OHD and the response variables considered by us. Conclusions: We observed a small positive correlation between a higher level of 25OHD and increased glycosylated hemolobin (HbA1c) or IR indices without clinical significance. Other modifiable or non-modifiable factors override 25OHD influence on IR in adult women with a normal serum level and may contribute to the remainder of the variability observed.

Subclinical hypothyroidism has no association with insulin resistance indices in adult females: A case‑control study

“…The data regarding insulin sensitivity and resistance in the course of thyroid dysfunctions remain controversial (11,22,(26)(27)(28). In a previous cross-sectional study in the Romanian population, Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) predicted a thyroid-stimulating hormone (TSH) increase in obese patients with newly diagnosed thyroid pathology (29).…”

“…Assuming that the probability of the exposure variable (hypothyroidism) in women from the general population is ~8% (21), with a 1:1 ratio for cases and controls, a prevalence of 25% of IR (22), and 80% power, a minimum (total) sample size of 150 was necessary for a univariate logistic regression model using a score test and a minimum (total) sample size of 187 for the same model using a Wald test, to be able to detect an odds ratio of 4 (log OR, 1.39). For the multivariate analysis, the sample size needed was much larger, but the pilot study data allowed for the assessment of such a study and more precise calculations for such a study.…”