Gonadotropin levels in urine during early postnatal period in small for gestational age preterm male infants with fetal growth restriction

The Impact of Maternal Gestational Diabetes Mellitus on Minipuberty in Boys

BACKGROUND/OBJECTIVES

Minipuberty is thought to play an important role in the sexual maturation of infants. Maternal disorders during pregnancy were found to have an impact on the activity of the reproductive axis in the first year of life. This prospective, matched, cohort study was aimed at investigating whether the course of minipuberty in boys is affected by maternal gestational diabetes mellitus (GDM).

METHODS

The study population consisted of three matched groups of boys: infants born to women with poorly controlled GDM, sons of women with adequately controlled GDM, and infants of healthy women with normal carbohydrate tolerance during pregnancy (control group). Salivary levels of testosterone, androstenedione, DHEA-S and estradiol, and urinary concentrations of FSH and LH were repeatedly measured over the first 12 months of life. Hormone levels were correlated with the size of genital organs (testicular volume and penile length), which were measured at each visit.

RESULTS

Compared with the remaining groups, the male offspring of women with poorly controlled GDM were characterized by higher concentrations of both gonadotropins, higher salivary testosterone levels, lower salivary DHEA-S concentrations, and longer periods of detection for LH and testosterone. Levels of gonadotropin, testosterone and DHEA-S in sons of mothers with poorly controlled GDM correlated with mean levels of glycated hemoglobin during pregnancy. Moreover, the infant boys assigned to this group were characterized by larger sizes of the testes and penis. Over the entire study period, there were no differences in hormone levels, testicular volume and penile length between sons of adequately treated women with GDM and sons of healthy women.

CONCLUSIONS

The obtained results indicate that GDM, if poorly controlled, may affect the activity of the reproductive axis and postnatal growth of male genital organs in the offspring.

Mini-Puberty, Physiological and Disordered: Consequences, and Potential for Therapeutic Replacement

There are 3 physiological waves of central hypothalamic-pituitary-gonadal (HPG) axis activity over the lifetime. The first occurs during fetal life, the second-termed "mini-puberty"-in the first months after birth, and the third at puberty. After adolescence, the axis remains active all through adulthood. Congenital hypogonadotropic hypogonadism (CHH) is a rare genetic disorder characterized by a deficiency in hypothalamic gonadotropin-releasing hormone (GnRH) secretion or action. In cases of severe CHH, all 3 waves of GnRH pulsatility are absent. The absence of fetal HPG axis activation manifests in around 50% of male newborns with micropenis and/or undescended testes (cryptorchidism). In these boys, the lack of the mini-puberty phase accentuates testicular immaturity. This is characterized by a low number of Sertoli cells, which are important for future reproductive capacity. Thus, absent mini-puberty will have detrimental effects on later fertility in these males. The diagnosis of CHH is often missed in infants, and even if recognized, there is no consensus on optimal therapeutic management. Here we review physiological mini-puberty and consequences of central HPG axis disorders; provide a diagnostic approach to allow for early identification of these conditions; and review current treatment options for replacement of mini-puberty in male infants with CHH. There is evidence from small case series that replacement with gonadotropins to mimic "mini-puberty" in males could have beneficial outcomes not only regarding testis descent, but also normalization of testis and penile sizes. Moreover, such therapeutic replacement regimens in disordered mini-puberty could address both reproductive and nonreproductive implications.

Minipuberty in Sons of Women with Low Vitamin D Status during Pregnancy

Minipuberty is a transient phase of reproductive axis activation during the first several months of life, playing an important role in the development of reproductive organs in boys. Low 25-hydroxyvitamin D levels during pregnancy are associated with an increased risk of neonatal complications. An inadequate gestational vitamin D status is hypothesized to affect the postnatal activation of the hypothalamic-pituitary-gonadal axis. The purpose of our study was to assess whether a low vitamin D status during pregnancy determines the course of minipuberty in boys. The study included three groups of male infants born to women with different vitamin D statuses: sons of women with vitamin D deficiency (group 1), sons of women with vitamin D insufficiency (group 2), and male offspring of females with normal 25-hydroxyvitamin D levels (group 3 (the reference group)). Concentrations of testosterone, androstenedione, dehydroepiandrosterone sulfate, estradiol, progesterone, and 17-hydroxyprogesterone in saliva, as well as concentrations of gonadotropins in urine, were assayed monthly from postnatal months 1 to 6, and once every 2 months in the second half of the first year of life. Additionally, at each visit, penile length and testicular volume were assessed. Concentrations of testosterone, FSH, and LH, as well as penile length and testicular volume, were greater in group 1 than in groups 2 and 3. In turn, group 2 was characterized by higher FSH levels and a greater testicular volume than group 3. Peak concentrations of LH and testosterone were observed earlier in group 1 than in the remaining groups. The obtained results suggest that a low vitamin D status during pregnancy may have a stimulatory impact on reproductive axis activity and on the early postnatal development of male genital organs, correlating with the severity of hypovitaminosis D.

Minipuberty in born small for gestational age infants: A case control prospective pilot study

PURPOSE

To evaluate minipuberty (MP) in small for gestational age (SGA) infants, both preterm and full-term, during the first year of life.

METHODS

33 SGA healthy newborns (group A), 21 of which full-term (subgroup A1) and 12 preterm (A2) were enrolled. Control group (B) consisted of 27 AGA, 17 full-term (subgroup B1) and 10 preterm (B2) infants. Growth parameters, FSH, LH, and Estradiol (E2) or Testosterone (T) serum levels were monitored at 3, 6, and 12 months.

RESULTS

The gonadotropin surge reached greater increase of LH in males at 3 months and FSH in females at 3, 6 and 12 months (p < 0.001). In male infants: T at 3 months was higher in subgroup A2 vs A1(p = 0.001), and correlated negatively with gestational age (GA, p < 0.005), length and weight at birth (p < 0.05); LH was higher in subgroup B2 vs B1 at 6 months (p = 0.003), and in group A vs B at 12 months (p = 0.03). Females displayed higher E2 at 6 months in B2 vs B1 (p < 0.05), negatively correlated with GA and weight gain (p < 0.05); LH at 6 months was increased in A2 vs A1 (p = 0.03). Overall, preterm males displayed higher T at 3 months (p = 0.001), LH at 3, 6 and 12 months (p < 0.05), and LH/FSH ratio at 6 months (p = 0.001). Preterm females exhibited increased LH/FSH ratio at 3 and 6 months (p < 0.05).

CONCLUSIONS

Irrespectively of GA, MP occurred with a typical sexual dimorphism and exhibited sex-specific correlations between hormones and perinatal parameters. SGA condition and prematurity seemed to enhance and protract MP over time in both sexes.

Cohort profile: The COPENHAGEN Minipuberty Study-A longitudinal prospective cohort of healthy full-term infants and their parents

BACKGROUND

The hypothalamic-pituitary-gonadal (HPG) axis governs sexual maturation and reproductive function in humans. In early postnatal life, it is transiently active during which circulating sex steroids reach adult levels. While this so-called minipuberty represents a universal phenomenon in infants of both sexes, its role for early maturation and growth remains incompletely understood.

OBJECTIVES

To provide normative data on auxology as well as serum and urinary hormone levels in healthy, full-term infants throughout the first year of life and to investigate associations of postnatal HPG axis dynamics as well as hormonal, genetic and environmental exposures with early genital development and growth.

POPULATION

Healthy, Danish, full-term, singleton newborns including their parents.

DESIGN

Single-centre, prospective, observational longitudinal pregnancy and birth cohort.

METHODS

Newborns were followed with six repeated clinical examinations during a one-year follow-up period. An umbilical cord blood sample was drawn at birth. At each visit, infants underwent a clinical examination focusing on auxology and genital development. Further, blood (serum, plasma, DNA) and urine samples were collected at each visit. Mothers and fathers underwent a clinical examination and provided blood samples prior to and after birth. A subset of parents provided urine samples and breast milk samples. Pregnancy and obstetrical outcomes, and detailed parental questionnaires were compiled.

PRELIMINARY RESULTS

Between August 2016 and August 2018, 2481 women with singleton pregnancies were invited to participate of which 298, including their partners, were enrolled (12.0%). A total of 268 healthy, full-term newborns born appropriate for gestational age (AGA) were included at birth, 233 newborns participated in the postnatal follow-up period and 186 completed the one-year follow-up period (9.4% and 7.5%, respectively).

CONCLUSION

The COPENHAGEN Minipuberty Study provides detailed, longitudinal data on early genital development and growth including hormonal and genetic profiles and environmental exposure in healthy infants including additional data in their parents.

Minipuberty: Looking Back to Understand Moving Forward

Hypothalamic-pituitary-gonadal (HPG) axis activation occurs three times in life: the first is during fetal life, and has a crucial role in sex determination, the second time is during the first postnatal months of life, and the third is with the onset of puberty. These windows of activation recall the three windows of the "Developmental Origin of Health and Disease" (DOHaD) paradigm and may play a substantial role in several aspects of human development, such as growth, behavior, and neurodevelopment. From the second trimester of pregnancy there is a peak in gonadotropin levels, followed by a decrease toward term and complete suppression at birth. This is due to the negative feedback of placental estrogens. Studies have shown that in this prenatal HPG axis activation, gonadotropin levels display a sex-related pattern which plays a crucial role in sex differentiation of internal and external genitalia. Soon after birth, there is a new increase in LH, FSH, and sex hormone concentrations, both in males and females, due to HPG re-activation. This postnatal activation is known as "minipuberty." The HPG axis activity in infancy demonstrates a pulsatile pattern with hormone levels similar to those of true puberty. We review the studies on the changes of these hormones in infancy and their influence on several aspects of future development, from linear growth to fertility and neurobehavior.

Ontogeny of Hypothalamus-Pituitary Gonadal Axis and Minipuberty: An Ongoing Debate?

The fetal hypothalamus-pituitary gonadal (HPG) axis begins to function during mid-gestation but its activity decreases during late pregnancy due to the suppressive effects of placental estrogens. Placental hormones drop immediately after birth, FSH and LH surge at around 1 week and peak between 1 and 3 months of life. The HPG axis is activated in both sexes, but a sexual dimorphism is evident with higher LH values in boys, while FSH prevails in girls. Both gonadotrophins decline in boys by around 6 months of age. In girls, LH declines at the same time as in boys, while FSH persists elevated up to 3 or 4 years of age. As a result of gonadotropin activation, testicular testosterone increases in males and ovarian estradiol rises in females. These events clinically translate into testicular and penile growth in boys, enlargement of uterus and breasts in girls. The functional impact of HPG axis activity in infancy on later reproductive function is uncertain. According to the perinatal programming theory, this period may represent an essential programming process. In boys, long-term testicular hormonal function and spermatogenesis seem to be, at least in part, regulated by minipuberty. On the contrary, the role of minipuberty in girls is still uncertain. Recently, androgen exposure during minipuberty has been correlated with later sex-typed behavior. Premature and/or SGA infants show significant differences in postnatal HPG axis activity in comparison to full-term infants and the consequences of these differences on later health and disease require further research. The sex-dimorphic HPG activation during mid-gestation is probably responsible for the body composition differences observed ad birth between boys and girls, with boys showing greater total body mass and lean mass, and a lower proportion of fat mass. Testosterone exposure during minipuberty further contributes to these differences and seems to be responsible for the significantly higher growth velocity observed in male infants. Lastly, minipuberty is a valuable "window of opportunity" for differential diagnosis of disorders of sex development and it represents the only time window before puberty when congenital hypogonadism can be diagnosed by the simple analysis of basal gonadotropin and gonadal hormone levels.

Up-To-Date Review About Minipuberty and Overview on Hypothalamic-Pituitary-Gonadal Axis Activation in Fetal and Neonatal Life

Minipuberty consists of activation of the hypothalamic-pituitary-gonadal (HPG) axis during the neonatal period, resulting in high gonadotropin and sex steroid levels, and occurs mainly in the first 3-6 months of life in both sexes. The rise in the levels of these hormones allows for the maturation of the sexual organs. In boys, the peak testosterone level is associated with penile and testicular growth and the proliferation of gonadic cells. In girls, the oestradiol levels stimulate breast tissue, but exhibit considerable fluctuations that probably reflect the cycles of maturation and atrophy of the ovarian follicles. Minipuberty allows for the development of the genital organs and creates the basis for future fertility, but further studies are necessary to understand its exact role, especially in girls. Nevertheless, no scientific study has yet elucidated how the HPG axis turns itself off and remains dormant until puberty. Additional future studies may identify clinical implications of minipuberty in selected cohorts of patients, such as premature and small for gestational age infants. Finally, minipuberty provides a fundamental 6-month window of the possibility of making early diagnoses in patients with suspected sexual reproductive disorders to enable the prompt initiation of treatment rather than delaying treatment until pubertal failure.