Increased PRL-reserve in hypogonadal patients during puberty. – Evidence for negative feed-back regulation during puberty?

Abstract

Hypophyseal hormones' secretion was stimulated by a test procedure using simultaneously TRH, LH-RH, and insulin in 3 hypoand 9 agonadal patients aged 8-16 ys, with bone ages ranging from 8-14 ys. The results were compared to those of 10 normal prepubertal and 6 pubertal subjects. PRL, TSH, LH, FSH, and HGH were measured by RIA, for PRL the Serono Kit was used. In normal children (C) and adolescents (A) PRL increased to maxima from 15-50 (♀) or 18-44 (♂) ng/ml after 15-60 min. No difference was observed between C and A or between ♀ and ♂. 5 out of 8 girls with Turner's syndrome showed exaggerated PRL-responses at 60min (26-84 ng/ml), 3 of them also at 15-30 min (64-85 ng/ml). Similar results were observed in 1 agonadal boy and 2 boys with Klinefelter's syndrome. The 60min value, in particular, was greatly elevated compared to results in normal boys (33-78 vs 8-25 ng/ml) This difference could not be attributed to variations of the hypoglycaemic responses. The peak PRL concentrations were positively correlated to the basal LH and FSH concentrations (r=0,80, n=10) in the hypogonadal patients, but not in the normal children. From these results it is concluded that in patients with diminished gonadal function the lack of gonadal steroids during puberty may lead to an increased PRL reserve of the pituitary gland. The significance of this finding remains to be determined.

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