The relationship of plasma gonadotrophins and androgen concentrations to body growth in boys

Abstract

Plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), 17 alphahydroxyprogesterone (17\g=a\-OPH),androstenedione (\ g=D\ 4) and testosterone (T) were measured in 543 healthy boys aged 6.0 to 15.9 years (with weight and height between the 3rd and 97th percentile for Mexican standards) as a function of chronologic age (CA), weight, height, surface area (SA) and calculated lean body mass (LBM) and total body fat (TBF).The earliest hormonal event was a clear rise in plasma 17\g=a\-OHP, either prior or simultaneously to at steady increase in plasma FSH, far ahead of any sign of puberty. These changes were closely followed by a continuous rise in plasma \ g=D\ 4. Thereafter, there was a prolonged period of low but progressively increasing plasma FSH levels in the face of constantly low LH levels. However, a brisk rise in plasma LH and FSH occurred at a mean weight of 35.4 kg, at a height of 144.5 cm and when LBM was 32.0 kg. Simultaneously, plasma 17\g=a\-OHP began to fall, \ g=D\ 4 reached a plateau and soon after, a marked rise in plasma T was documented. When plasma LH and FSH concentrations were plotted against CA, weight, height, SA and LBM a significant quadratic equation was disclosed in each case. Both gonadotrophins did not correlate with TBF. Multiple variance analysis demonstrated that LBM and SA had the most marked effect on LH, while LBM was the most important variable affecting plasma FSH concentrations. The present data suggest the association between a "critical level" of body composition and the major hormonal events in boys, regardless of a causeeffect relationship. A critical level of LBM (20\p=n-\23 kg) and not of TBF was attained at time of the initial hormonal changes, as well as at the time of the major changes in plasma gonadotrophins (32\p=n-\35 kg).

The relationship of plasma gonadotrophins and steroid concentrations to body growth in girls

“…Furthermore, the principal hor¬ monal events occur earlier in girls than in boys on a basis of age, weight or height (Parra et al 1981). It is interesting to observe that both in boys (Parra et al 1981) and girls (present study) the initial and subsequent hormonal changes occurred in associa¬ tion with a similar level of LBM: 22-24 and 30-34 kg, respectively.…”

“…Furthermore, the principal hor¬ monal events occur earlier in girls than in boys on a basis of age, weight or height (Parra et al 1981). It is interesting to observe that both in boys (Parra et al 1981) and girls (present study) the initial and subsequent hormonal changes occurred in associa¬ tion with a similar level of LBM: 22-24 and 30-34 kg, respectively. This information would agree with the suggestion that LBM has a closer association than TBF with the initiation and pro¬ gression of puberty (Frisch et al 1977;Wilen & Naftolin 1977).…”

“…We describe changes in the plasma concentra¬ tions of gonadotrophins and some steroids in 352 clinically healthy girls aged 6.0 to 15.9 years, as a function of age, body weight, height, calculated (Parra et al 1980a(Parra et al ,c, 1981.…”

Plasma gonadotrophins profile in relation to body composition in underprivileged boys

“…The gonadotrophin data in healthy boys have been described extensively in a previous publica¬ tion (Parra et al 1981), and their plasma gonado¬ trophin changes will be discussed only in com¬ parison with the changes observed in UP boys. Based on chronological age, mean plasma FSH concentrations in UP boys were not only lower than normal from 11.0 to 13.9 years, but the steep rise in this hormone occurred 2 years later than in healthy boys.…”

“…This observation seems fur¬ ther to support the hypothesis of a closer associa¬ tion between a 'critical' level of LBM (and not of body fat) and the initiation of puberty (Wilen & Naftolin 1977;Frischetal. 1977;Parra et al 1981). …”