Clinical characteristics of preterm ovarian hyperstimulation syndrome: seven cases from China and 14 cases from the literature

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.

In Memory of Ivo Brosens: Reflections on the Pathophysiology of Neonatal Uterine Bleeding

BACKGROUND

The occurrence of vaginal bleeding in early neonatal life has been observed for centuries and was considered a consequence of the sudden drop in circulating hormones following birth. As such, neonatal uterine bleeding was dismissed as having no clinical significance. Interest in the phenomenon was renewed when a new theory suggested a link between neonatal uterine bleeding (NUB) and accelerated endometrial maturation. This theory was based on the observation of a higher incidence of NUB in babies born post-term or after pregnancies complicated by intrauterine growth restriction, preeclampsia, or blood group incompatibility.

OBJECTIVE

The objective of this study was to review of available evidence on the pathogenesis of NUB.

METHOD

Review of available literature using Medline search (August 2022, no limit on start date or language) to identify articles that may link NUB with features of the uterus and/or endometrium.

OUTCOME

The fetal endometrial responses differ from that of the adult. In the fetus, the endometrium features progestogenic response only in a minority of cases. The endometrium in most newborn girls does not exhibit secretory or decidual changes which indicate lack of progesterone response. Most newborn girls do not have visible bleeding. Animal studies linked exogenous progestogen exposure during the period of organogenesis to poor endometrial gland development, progesterone resistance, and to alterations of reproductive performance. Although the fetal endometrium may not exhibit a full proliferative response, it is clearly sensitive to circulating estrogens. Molecular mechanisms involved in NUB may include "ontogenetic progesterone resistance."

CONCLUSION AND OUTLOOK

Endometrial development and its response to withdrawal of hormones at birth varies and may be affected by intrauterine stressors and gestational age. Factors that affect endometrial development during fetal life and in preterm neonates can have implications on future reproductive performance.

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.