Assessment of physiological factors for the establishment of serum insulin reference intervals in healthy Chinese Han adults: A community-based large cross-sectional study

The relationship between anti-Müllerian hormone serum level and body mass index in a large cohort of infertile patients

PURPOSE

To evaluate the relationship between serum Anti-Müllerian hormone (AMH) level and body mass index (BMI) in infertile patients.

METHODS

Medical records of patients with infertility evaluated between January 2013 and February 2018 in the Reproductive Medicine Department of a private hospital were reviewed. Patients with the following criteria were excluded from the study: polycystic ovary syndrome, primary ovarian insufficiency, AMH values > 10 ng/mL, current oral contraceptive users and previous ovarian surgery or endometriosis, and anovulation of other causes, except decreased ovarian reserve.

RESULTS

A total of 2204 infertile patients were included (mean age 34.58 ± 4.3 years, mean BMI 22.35 ± 3.6 kg/m², and mean serum AMH 2.44 ± 2.17 ng/ml). In the entire group of patients, serum AMH level was positively correlated with BMI after adjustment for age (beta = 0.059, p < 0.005). When the association between serum AMH level and BMI was analysed in subgroups of patients, after adjustment for age, we found a positive correlation between the two parameters in patients ≤ 35 years old (< 0.05), of normal weight (p < 0.05) and with normal ovarian reserve (p < 0.05). After adjustment for age, BMI ≥ 25 kg/m² was significantly associated with higher AMH values in comparison to normal weight patients.

CONCLUSIONS

In infertile patients, AMH is positively correlated with BMI, especially in patients younger than 35 years, of normal weight and with normal ovarian reserve. Moreover, the presence of mild excess adiposity seems to be associated with higher AMH values. Our data contradict the previous studies showing a negative impact of excess adiposity on AMH serum levels.

Assay-dependent variability of serum insulin concentrations: a comparison of eight assays

Although insulin measurement is essential for both clinical and research purposes, there is currently no reference method for insulin assays. The aim of this study was to compare results of serum insulin determined by a number of commercially available assays. We compared eight insulin assays by analyzing 165 serum samples. Assays included two chemiluminescence (Roche and DiaSorin), four ELISA (Tosoh, Mercodia, Monobind, and Diametra), and two IRMA (Izotop and BioSource) methods. Each assay was compared with the mean of all assay methods and Bland-Altman difference plots were used to measure agreement between each assay and overall mean. Least squared perpendicular distance regression analysis (Deming's method) was used to calculate slope and intercept for bias and also for each assay vs. mean of eight assays. Findings showed that the lowest and highest median insulin concentrations varied by a factor of 1.8. Maximum and minimum correlations with mean of assays were observed for Roche (0.992) and BioSource (0.844), respectively. Significant bias was observed in six assays. In pairwise comparisons of different assays, the highest and least mean differences were 7.78 μU/mL and -0.14 μU/mL, respectively. In conclusion, serum insulin measurement with different assays showed a maximum of 1.8-fold difference, a point that should be taken into consideration in the interpretation of circulating insulin levels in both clinical and research fields.