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


 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.


Introduction
Physical breast development is named according to age and sex as telarche, gynecomastia, breast growth, breast enlargement, breast swelling, and breast hypertrophy. There is no proper medical terminology for physiological enlargement of breasts in the newborn. In this article, the term "breast enlargement" will be used. Breast enlargement does not occur in all newborns. Breast enlargement is seen in 65-90% of all newborns as a possible consequence of the continuing action of estrogens, progesterone, and mammotropic peptides that characterize the intrauterine environment. Breast enlargement usually resolves spontaneously a few weeks after birth, coinciding with the withdrawal of maternal hormones 1 . The breast tissue contains estrogen and androgen receptors. The estrogen-toandrogen balance is suggested to play an essential role in breast enlargement 2 . Mini-puberty in babies can cause an imbalance between estrogen and androgen concentrations 3 . Inequality in the serum concentrations or synthesis of androgen or estrogen can lead to gynecomastia or premature telarche 4 .
The Sex Hormone Binding Globulin (SHBG) plays a crucial biological role in regulating sex hormones.
SHBG affects the function of some sex hormones, including testosterone and estrogen. Any change in SHBG level leads to an imbalance between estrogen and testosterone. Increased SHBG concentrations lead to lower free testosterone concentrations 1,5 . The SHBG binds androgens with higher a nity compared to estrogen 4 .
The free androgenic index (FAI) is calculated as [Total Testosterone x 100/SHGB]. Normal FAI in children is <5. It is used in the diagnosis of hyperandrogenemic conditions such as hirsutism 6 .
This study aimed to analyze Body Mass Index (BMI), Estrogen, Testosterone, SHBG levels, FAI, and Estrogen/Testosterone ratio (E/T) levels' in uence in newborn breast enlargements. Additionally, we de ned the mean, minimum, maximum, standard deviation, and percentiles of SHBG and FAI in 14-28 days-old babies.

Methods
This prospective study was performed to determine the weight, length, BMI, serum Estrogen, Testosterone, E/T ratio, SHBG, and FAI levels in babies presenting with breast enlargement to the Erzurum Atatürk University Faculty of Medicine Research Hospital Pediatric Endocrinology Clinic in Turkey. The study was approved by the university's ethical committee (Atatürk University, Faculty of Medicine, Ethical Committee. Session 7, Decision number: 62). Study purpose and methods were explained to all families, and their permissions were obtained.
Forty babies with breast enlargement aged 14-28 days (17 boys and 23 girls) were included in the study group, while 36 babies in the same age group (19 boys and 17 girls) were included in the control group.
All babies were completely healthy except for breast enlargement. Babies were excluded if born between 38 and 42 weeks, had any congenital abnormality or chronic illnesses, and if a chronic disease was present in the mother. Breast enlargement was evaluated based on the highest breast diameter. The diameter was >1 cm in all breast enlargement patients included in the study. Babies with the highest breast diameter of 0-1 cm were excluded. Cases with the highest breast diameter of 0 cm were included in the control group. Babies between 14-28 days old were specially selected to ensure standardization.
The serum samples were analyzed in the Atatürk University Health, Research, and Application Hosptital Biochemical Laboratory with the DXI800 hormone analyzer using the chemiluminescent method.

STATISTICAL ANALYSIS
The numerical data were expressed as mean, minimum, maximum, and standard deviation. Extreme values were removed. The SPSS 20 Program for Windows was used for the results. The One-Sample Kolmogorov-Smirnov test was used to determine whether numerical data in the breast enlargement and control groups were distributed normally. According to the One-Sample Kolmogorov-Smirnov test, the distribution of weight, height, BMI, testosterone, SHBG, and FAI levels of all participants were assessed to be normal. The Independent-sample T-test was used to make comparisons. According to the One-Sample Kolmogorov-Smirnov test, the distribution of estradiol and E/T levels was abnormal. The non-parametric alternative Mann-Whitney U test was applied to compare these data. The SHBG and FAI values were calculated as mean, minimum, maximum, standard deviation, and percentages for 14-28 days-old newborns. The Pearson Chi-square test was used to determine whether there was a signi cant relationship between breast enlargement and sex. P≤0.05 was considered signi cant.

Results
Forty newborns (23 girls (57.5%) and 17 boys (42.5%)) were included in the study group. The study group's mean values were: age 20.30±3.86 days (14- When our cases were evaluated according to breast enlargement, there were no signi cant differences in estrogen (p=0.696), testosterone (p=0.502), SGBG (p=0.753), and FAI (p=0.735) levels between the test and control group. There were no signi cant differences in chronological age (p=0.472), weight (p=0.197), height (p=0.268), body mass index (p=0.483), E/T ratio (p=0.868), and blood variables between the study and control group. It was concluded that newborns' breast enlargement is independent of weight, length, body mass index, estrogen, testosterone, SHBG, FAI, and E/T ratio.
Our case's laboratory values were also evaluated according to sex. According to the independent-sample T-test, testosterone (p<0.001) and FAI (p<0.001) were signi cant regarding sex, but SHBG (p=0.784) was not signi cant. According to the Mann-Whitney U test, E/T ratio (p<0.001) was signi cant concerning sex, but estradiol (p=0.387) was not signi cant.
In the Pearson Chi-square test, no signi cant correlation was found between sex and breast enlargement (p=0.370). While a signi cant relationship was found between sex and testosterone, FAI, and E/T, no signi cant relationship was found with estradiol. No signi cant relationship was found between sex and breast enlargement. It was concluded that newborn breast enlargement is independent of sex and estradiol. The SHBG and FAI values are shown as mean, standard deviation, minimum, maximum, and 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles in Table 1. Various studies on the SHBG levels of children have been conducted, but no studies analyzed the plasma SHBG levels of newborns with breast enlargement. SHBG levels were high in premature telarche girls 8 . SHBG levels and FAI are more sensitive markers both in the etiology of gynecomastia and in the onset of puberty in boys 9,10 . In a study of pubertal gynecomastia, chronological age, height, BMI, serum estradiol, testosterone, and SHBG levels did not signi cantly differ between the pubertal gynecomastia group and the control group 10 .
One study found that the gynecomastia group had lower testosterone levels and higher BMI, but these differences between gynecomastia and control groups were not statistically signi cant 11 .
In a study of 536 adolescents with gynecomastia, comparison with the control/test groups revealed no difference in serum estradiol, testosterone levels, E/T ratio, and estrogen/DHEAS ratio. However, lower free testosterone levels, weight, BMI, and higher SHBG levels were observed in gynecomastia patients 12 .
In our study, estrogen levels, testosterone levels, and SGBH levels were lower in the test group. Additionally, FAI levels, E/T ratio, and BMI were high. However, chronological age, sex, weight, height, BMI, estrogen, testosterone, SHBG, FAI, and E/T ratio levels were not statistically signi cant in newborn breast enlargements. In our study, there was no signi cant difference in the SHBG levels of the study and control groups. This result shows similarities with the results found in adults with gynecomastia and premature telarche patients.
It is known that increased free testosterone and FAI levels reduce the risk of gynecomastia 10,13 . In our study, FAI levels were higher in the breast enlargement group. However, no signi cant differences in FAI levels were determined between the study and the control groups.
There are differences in the levels of the SHBG concentration in the blood circulation concerning sex, and SHBG levels of females are generally higher than males. In healthy children, SHBG was signi cantly negatively correlated with testosterone, estradiol, dehydroepiandrosterone sulfate, and BMI in boys.
However, only dehydroepiandrosterone sulfate and BMI were negatively correlated in girls 14 .
In our study, no signi cant relationship was found between sex and estrogen and SHBG. However, a signi cant relationship was found between sex and testosterone, FAI, and E/T ratio. As a result, no signi cant relationship was found between sex and breast enlargement. There is no difference between boys and girls. Neonatal breast enlargement is independent of sex.
Neonatal breast enlargement is independent of weight, height, body mass index, estrogen, testosterone, SHBG, FAI, and E/T ratio.
The number of studies on neonatal breast enlargement is very limited. We have done a similar study previously 15 . In our previous study, Kisspeptin, follicle-stimulating hormone, luteinizing hormone, estradiol, and prolactin were studied. Kisspeptin, prolactin, and luteinizing hormone were signi cant but estradiol and follicle-stimulating hormone were not signi cant in this study 15 .
Although estradiol is an effective hormone in normal pubertal telarche, it is ineffective in neonatal breast enlargement.
The reasons for this can be explained as follows: a-neonatal ovaries have different estrogen secretion b-due to the decline of maternal estradiol after birth, the real-time estradiol level in the blood is not the same c-despite decreased estradiol, the reduction in breast tissue that could not catch decreased estradiol levels d-the real-time estriol and estrone levels in the blood cannot be known This is related to the fetus getting exposed to high concentrations of estrogen, primarily estriol, produced by the mother and the placenta 4 .
In our study, we have studied the effects of estradiol, not estriol and estrone combined. We could not nd the effect of estradiol alone on breast enlargements in newborns. This situation can be explained by the effect of estriol and mammotropic peptides crossing the placenta that newborns' breasts enlarged beforehand. This study revealed the importance of other types of estrogen detection in neonatal breast enlargement.
Another aim of our study was to de ne the normals and percentiles of SHBG and FAI in newborn babies according to sex. According to our knowledge, SHBG normal and FAI normal have been de ned in only one study in newborn infants 16  The limitations of the study are determining estradiol only and the relatively low number of cases. Also, follicle stimulating hormone, luteinizing hormone, and prolactin were not studied because they were investigated in our previous study 15 .

Conclusion
In our study, normal values and 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles of SHBG and FAI were de ned according to sex. It was concluded that neonatal breast enlargement is independent of weight, height, body mass index, estrogen, testosterone, SHBG, FAI, E/T ratio, and especially sex. Our study has provided new information about newborn breast enlargements. In the physiology of neonatal breast enlargement, there are still situations that await clari cation. Our study has revealed the need for large controlled studies on the physiology of breast enlargement in newborns.

Abbreviations
Sex Hormone Binding Globulin (SHBG), free androgenic index (FAI), Body Mass Index (BMI), Estrogen/Testosterone ratio (E/T) Declarations Funding: No funding was secured for this study.
Con ict of Interest: The authors have no con icts of interest to disclose.
Availability of data and material: Not applicable