Integrated concentrations of follicle stimulating hormone and puberty

Pattern of secretion of bioactive and immunoreactive gonadotrophins in normal pubertal children

OBJECTIVE

The aim was to investigate the relationship between the nocturnal pulsatile secretory patterns of immunoreactive and bioactive luteinizing hormone in normal children at various stages of puberty.

DESIGN

Blood samples were taken at 15-minute intervals from 2000 hours to 0800 hours. Pubertal stage was assessed by the method of Tanner (1962).

PATIENTS

Thirty-four healthy siblings (17 males, 17 females) of diabetic children were recruited (median age 13.1, range 9.1-20.9 years). They were of normal height, non-obese, and covered the range of puberty.

MEASUREMENTS

Follicle stimulating and luteinizing hormone levels were measured by radioimmunoassay in all 34 subjects; bioactive LH (B-LH) was assayed in a subgroup of 13 subjects selected to encompass the range of normal puberty. Oestradiol (girls) and testosterone (boys) were also measured at hourly intervals.

RESULTS

Immunoreactive luteinizing and follicle stimulating hormone concentrations showed a progressive rise during puberty in both sexes. FSH concentrations were significantly higher in females than in males at all stages of puberty. Overnight mean bioactive luteinizing hormone concentrations were higher than immunoreactive luteinizing hormone levels in all the girls studied (n = 7). Although the number of bioactive luteinizing hormone pulses (31) was greater than immunoreactive pulses (27), the profiles were generally very similar. In the early pubertal girls an increase in the bioactive: immunoreactive ratio was observed during the middle of the night with the onset of pulsatility. Oestrogen was detected in the girls in breast stage 4-5 but not in two of the early pubertal girls, despite pulses of immunoreactive and bioactive luteinizing hormone. The boys had higher mean bioactive than immunoreactive luteinizing hormone levels and overall bioactive and immunoreactive luteinizing hormone and testosterone concentrations increased with puberty stage. Concordance between bioactive and immunoreactive hormone pulses was good although more immunoreactive pulses (16) were seen than bioactive pulses (14). As in the girls, an increase in the bioactive: immunoreactive ratio was observed in the middle of the night with the onset of pulsatility at genital stage 2 but, in contrast to the oestrogen data in the girls, testosterone secretion always followed luteinizing hormone pulsatility overnight.

CONCLUSION

We conclude that mean overnight immunoreactive luteinizing and follicle stimulating hormone concentrations increase during puberty in both sexes. Bioactive luteinizing hormone levels are two to three times higher than immunoreactive luteinizing hormone in both sexes, but there is very little discordance between immunoreactive and bioactive luteinizing hormone pulsatility. The bioactive: immunoreactive ratio increases with the occurrence of pulsatility overnight in early pubertal children. The relationship between these changes in bioactive and immunoreactive luteinizing hormone and sex steroids is clearest in boys where the nocturnal testosterone rise always follows pulsatile LH secretion.

Growth and endocrine function after renal transplantation

Longitudinal height data and physical development were assessed in 45 boys and 34 girls after renal transplantation. All children received alternate day steroids and either azathioprine or cyclosporin A for immunosuppression. There was a significant increase in growth velocity after transplantation in prepubertal children. Growth velocity declined at the expected age of the normal pubertal growth spurt, however, with delay in the appearance of secondary sexual characteristics. Overnight hormone profiles in 17 adolescent subjects with short stature or maturational delay, or both, showed blunting of growth hormone and gonadotrophin pulsatility. It is likely that long term steroid treatment after renal transplantation induces the clinical and endocrine picture of delayed puberty. Failure of growth to accelerate at this time is a cause of short stature, which may have an effect on adult height.

Growth and endocrine function in steroid sensitive nephrotic syndrome

Longitudinal height data and physical development were assessed in 29 boys and 12 girls taking long term steroid treatment for steroid sensitive nephrotic syndrome. Growth in both boys and girls, assessed by changes in height standard deviation score (delta Ht SDS), worsened significantly with chronological age. There was a significant negative correlation between delta Ht SDS and duration of treatment in boys, but not in girls. There was no correlation between delta Ht SDS and relapse rate or the use of cyclophosphamide. In the boys, Ht SDS decreased significantly only after the age of 10 years and was associated with delay in the appearance of secondary sexual characteristics. Eight adolescent boys were assessed endocrinologically by an overnight hormone profile. Blunting of the pulsatility of growth hormone and gonadotrophins was seen in six. Normal profiles were seen in two subjects who were both off steroid treatment at the time of study. Abnormal endocrine function in adolescent boys treated long term for steroid sensitive nephrotic syndrome corresponded with the clinical picture of delayed onset of puberty, which accounted for severe growth retardation in a substantial proportion of subjects.

Sexual maturation of the hypothalamus: pathophysiological aspects and clinical implications

Sexual maturation in humans begins early in fetal life and culminates in adulthood when the gonads have acquired a full capacity for reproduction. It is remarkable that during this long process, the pituitary gonadal function, hence its hypothalamic control presents an alternative of activation and inhibition periods, during which the interrelations of the 3 components of the hypothalamic-pituitary-gonadal axis change gradually and inversely. The ontogeny of the hypothalamic-pituitary system, the varying activity of the reproductive endocrine system throughout sexual maturation and the developmental changes in the interrelations of the hypothalamic-pituitary-gonadal axis are reviewed: the most striking feature of human sexual development is the long inhibition of hypothalamo-pituitary function during childhood. Much indirect evidence points to the determining role of the CNS in the maturation of hypothalamic function: the occurrence of rhythms of secretion, the amplitude of secretions and peripubertal specific sleep-related nycthemeral rhythm of secretion at the onset of puberty. Despite the reality of a negative feedback control, these changes do occur independently of gonadal secretions since they are observed (qualitatively if not strictly quantitatively) in agonadal children. It is likely that neurotransmitters (dopamine, serotonine) and opiates have an inhibitory effect on Gn-RH release. But we still don't know their evolution during sexual maturation. It does not appear that melatonine plays any determinant role in the onset of human puberty. The clinical implications of our present understanding of the physiological events occurring during sexual maturation are several. Considering the major problems related to abnormal sexual maturation we will discuss successively: (1) diagnosis of hypogonadotrophic hypogonadism in early infancy; (2) differential diagnosis between premature thelarche and true sexual precocity; (3) the usefulness of endocrine investigations in the evaluation of hypothalamic-pituitary function; and (4) the new developments in the treatment of precocious puberty, delayed puberty or hypogonadism.

Diurnal variations in estradiol binding site concentrations in the hypothalamus, pituitary and uterus of prepuberal rats

Available cytosolic estradiol binding sites (EBS) were estimated at 6 h intervals over a 24 h period in individual extracts of uteri, pituitaries and hypothalami from intact, ovariectomized or hypophysectomized 28-day old rats, maintained from birth in a 12 h light-12 h dark photoperiod. Plasma estrogen levels were also recorded, in intact rats, they displayed a 20% rise during daytime. In the uterus and pituitary of ovariectomized rats EBS concentrations exceeded by one third those of intact controls. In intact animals, significant diurnal variations in EBS were observed in both these tissues, with increased daytime levels. These variations appeared to depend on the amount of estrogen in the plasma, as they were not observed in spayed rats. No diurnal variations in EBS were apparent in the hypothalamus of intact animals, but they did occur in ovariectomized rats, and even more significantly in hypophysectomized rats, although the latter had lower EBS concentrations than spayed animals. These variations were presumed to result from the interference of pituitary-controlled hormones other than estrogens in the regulation of EBS levels.

Decreased LH response to the second of consecutive day luteinizing hormone releasing hormone (LHRH) in fusions among patients with constitutional delay of puberty: a phenomenon of pubertal maturation?

Consecutive day LHRH stimulation by continuous infusion has been used to evaluate pituitary reserve. Different responses on the 2 days were not present among non-pubertal hypopituitary patients, pubertal growth hormone deficient patients or adult males. However, patients with constitutionally delayed puberty demonstrated a greater serum LH response on day 1 than day 2. Urinary LH responses suggest a similar but not statistically significant pattern. This response may be a normal phenomenon of puberty or may represent part of the reason for constitutionally delayed puberty.

Adult height and fertility in men with congenital virilizing adrenal hyperplasia

The effects of congenital adrenal hyperplasia on adult height and fertility were studied in 30 afflicted men. The patients' heights ranged from 150.0 to 178.6 cm (mean +/- 1 S.D. of 164.0 +/- 7.6), which is significantly lower than both the mean adult height for American men and that of the patients' parents (P less than 0.005). There was no correlation between adult height and the age at which therapy was begun, possibly because the patients treated before one year of age had the salt-losing form of the syndrome. Therapeutic compliance may also have been involved. Apparently normal fertility, indicated by paternity and normal sperm counts, was found in 18 out of 20 patients evaluated. This group included five untreated patients who were found to be fertile and to have normal plasma testosterone and gonadotropin but elevated androstenedione levels.