Changes in Growth and Serum Growth Hormone and Plasma Soipatomedin-C Levels During Suppression of Gonadal Sex Steroid Secretion in Girls with Central Precocious Puberty*

Abstract

Suppression of gonadal sex steroid secretion in children with central precocious puberty (CPP) by LHRH analogs affords an opportunity to study sex steroid modulation of GH and somatomedin-C (Sm-C) secretion and to examine the role of GH and Sm-C in pubertal and prepubertal statural growth. Nocturnal serum GH and plasma Sm-C levels were measured in 10 preadrenarchal girls [mean age, 3.0 +/- 0.6] ( +/- SEM) yr with CPP before and during 2 yr of LHRH analog-induced gonadal suppression. Their mean height velocity, initially 4.6 +/- 0.6 ( +/- SEM) SD above the mean for chronological age, decreased to -0.1 +/- 0.4 SD during 12-24 months of ovarian suppression (P less than 0.00005). The mean peak nocturnal plasma GH level was 22.5 +/- 5.4 ( +/- SEM) micrograms/L during puberty, and it decreased to 10.2 +/- 2.1 micrograms/L after 3 months of suppression of gonadarche. This decrease persisted throughout the 2 yr of gonadal suppression (P less than 0.05). The reduction in GH secretion was accompanied by a decrease in mean plasma Sm-C levels from 3.5 +/- 0.7 to 1.5 +/- 0.2 U/mL after 3 months of suppression of gonadal sex steroids, which persisted during 2 yr of gonadal suppression (P less than 0.01). Suppression of ovarian function in girls with CPP results in decreased height velocity. This slowing of growth occurs in association with decreased nocturnal serum GH and plasma Sm-C levels, suggesting that acceleration of growth during puberty is partially mediated by sex steroid-induced augmentation of GH secretion.

Short-day melatonin pattern advances puberty in seasonally breeding rhesus monkeys (Macaca mulatta)

“…Correspondingly, the pattern ofGH and somatomedin-C secretion paralleled that of oestradiol. These results support the hypothesis that maturational increases in GH secretion may, in part, be due to increases in ovarian oestradiol secretion (Copelant et al, 1984;Mansfield et al, 1988), and that these two hormones act synergistically to enhance soma¬ tomedin-C secretion (Wilson, 1986). Nevertheless, greatest increases in GH occurred for Group females well before significant maturational increases in oestradiol had occurred (30 months), sug¬ gesting that maturational increases in GH are not due solely to increases in oestradiol.…”

Serum IGF1 and insulin levels in girls with normal and precocious puberty

“…Although this may indicate a direct effect of sex steroid withdrawal, GH secretion seems to be suppressed in parallel with the decrease in the activity of the hypothalamic-pituitary-gonadal (HPG) axis during GNRHa treatment (32). Accordingly, the positive influence of pubertal progression and E 2 priming on secretion of GH during stimulation testing is well documented (33).…”

GH as a co-gonadotropin: the relevance of correlative changes in GH secretion and reproductive state

“…The close relationship between GH and gonadal steroid levels during the pubertal period suggests that gonadal steroids may stimulate linear growth, in part, by stimulating pituitary GH secretion (Wennink et al 1991). Indeed, both gonadal steroid synthesis and the GH secretory pulse amplitude begin to increase earlier in girls with precocious puberty, and suppression of gonadal steroid secretion by gonadotropin-releasing hormone (GnRH) agonists in these girls also suppresses GH and insulin-like growth factor-I (IGF-I) secretion (Mansfield et al 1988). The somatotrophic axis must be activated by very small increases in circulating estrogens, since GH and IGF-I concentrations rise before the initiation of sexual development (Rose et al 1991) and very low doses of estrogens effectively increase GH secretion in hypogonadal states (Mauras et al 1990).…”