The Relationship of Serum Sex-Hormone Binding Protein and Free Androgen Index Levels to Newborn’s Breast Enlargement

Abstract Aim This study aimed to analyze body mass index, estrogen, testosterone, sex-hormone-binding-globulin (SHBG), free androgenic index (FAI), and estrogen/testosterone ratio and their relationship to breast enlargement in newborns. Additionally, we defined the mean, minimum, maximum, standard deviation, and percentiles of SHBG and FAI in 14-28 days-old babies. Methods Forty babies with breast enlargement aged 14-28 days (17 boys and 23 girls) were included in the study. As controls were taken 36 babies in the same age group (19 boys and 17 girls). The SHBG and FAI values were calculate as mean, minimum, maximum, standard deviation, and percentages in 14-28 days-old newborns. Normal values and 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles of the SHBG and FAI values were calculated according to sex. Results The mean, standard deviation, minimum, and maximum SHBG values among girls, boys, and all participants were 74.84±26.21 ng/dL (26.80-135.20 ng/dL), 73.22±24.98 ng/dL (13.00-144.80 ng/dL), and 74.07±25.48 ng/dL (13.00-144.80 ng/dL), respectively. The mean, standard deviation, minimum, and maximum FAI values of girls, boys, and all participants were 0.44±0.33 (0.03-1.38), 1.42±0.54 (0.69-3.46), and 0.91±0.66 (0.03-3.46), respectively. Conclusion Neonatal breast enlargement is not associated with weight, length, body mass index, estrogen, testosterone, SHBG, FAI, Estrogen/Testosterone ratio, or sex. In the physiology of neonatal breast enlargement, there are still situations that await clarification.