# Focus on the endocrine system of children born after reproductive technologies in Kazakhstan

## TL;DR

This study compares the endocrine and growth indicators of children born via reproductive technologies versus natural conception in Kazakhstan.

## Contribution

The study provides new evidence on the safety of reproductive technologies regarding children's endocrine and anthropometric outcomes.

## Key findings

- Children born naturally had higher body weight and height compared to those born via ART.
- ART children had slightly higher free T3, potassium, and glucose levels, but all within normal ranges.
- Correlations were found between body weight, height, and certain biochemical markers like insulin-like growth factor and T3.

## Abstract

Reproductive technologies are used more widely today than ever before. This increase in the use of assisted reproductive technology (ART) is directly related to sociodemographic conditions that result in delayed childbirth among age groups with lower fertility. Infertility affects 17% of married couples, and in some countries 6% of children are born with in vitro fertilization (IVF). In this context, the aspect of the influence of reproductive technologies on hormonal indicators of offspring in relation to anthropometric data remains insufficiently examined. The purpose of this cohort study is to compare the hormonal panel and anthropometric data of ART-conceived children with the corresponding data of children conceived naturally.

Biochemical tests are used to determine the amount of free triiodothyronine (T3) and total thyroxine (T4), somatotropin, insulin, insulin-like growth factor, glucose, potassium, and sodium cations in blood samples from the experimental and control groups.

The results indicate that the use of assisted reproductive technologies neither altered the endocrine panel of the thyroid gland, nor affected other biochemical parameters. Variations in technologies – classical IVF, fresh or frozen embryo transfer, intracytoplasmic sperm injection – also did not affect the quantitative value of the above indicators. Artificial insemination also had no effect on puberty (in both boys and girls). Children born naturally had a greater body weight (3,453 vs 3,160 g, p < 0.001) and height (53 vs 51 cm, p = 0.002). ART children had significantly higher median free tbl3 levels (3.65 vs 3.48 mU/L, p = 0.002) and potassium levels (4.8 vs 4.7 mmol/L, p = 0.013), although within the reference ranges. Glucose levels were also higher in ART children (median 4.45 vs 4.29 mg/dl, p = 0.01).

Several relationships between biochemical and anthropometric indicators were identified: the correlation between body weight and blood levels of insulin-like growth factor was statistically significant, positive, and weak. The tbl3 level in the experimental group was found to be statistically significant and directly proportional to body height, and insulin content was inversely proportional to body weight. The data obtained make it possible to verify the safety of using a different range of reproductive technologies.