LUTEINIZING HORMONE AND FOLLICLE STIMULATING HORMONE SECRETION PATTERNS IN BOYS THROUGHOUT PUBERTY MEASURED USING HIGHLY SENSITIVE IMMUNORADIOMETRIC ASSAYS

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Abstract
Pulsatile gonadotrophin secretion patterns were studied in 32 normal boys (chronological age, CA 7.2-14.6 years) at different stages of pubertal development (5 in stage G1, 11 in G2, 5 in G3, 4 in G4, 7 in G5). Plasma LH and FSH concentrations were measured at 10 min intervals from 1200 to 1800 h and from 2400 to 0600 h using an immunoradiometric assay with a lower limit of detection of 0.15 IU/1 for both LH and FSH. Plasma testosterone (T) was measured hourly. In the young prepubertal boys plasma LH was not detectable during day or night. In contrast, plasma FSH ranged from 0.7 to 1.4 IU/1. Plasma T was not detectable either (< 0.25 nmol/1). In the older prepubertal boys a discrete pulsatile LH pattern (2 per 6 h) became discernible only during the night (range 0.1-0.4 IU/1). Plasma FSH also revealed a pulsatile pattern only during the night (2 per 6 h), while plasma T still remained undetectable. In the early pubertal boys (G2) a median daytime LH value of 0.37 IU/1 was determined with 1 pulse per 6 h and at night definite LH pulses (4 per 6 h) were found in all boys (range 0.4-4.7 IU/1). Plasma FSH increased considerably to a median level of 2.50 IU/1 during the day; most boys had a pulsatile FSH pattern (one per 6 h). Plasma T became detectable during the day (median 0.54 nmol/l) and night (median 1.16 nmol/1). With the progression of puberty the mean plasma level of LH and FSH, the LH/FSH pulse number and the LH/FSH pulse amplitude increased; plasma T rose as well, more obviously during the night. In G5, however, the LH pulse number decreased, while the LH level and pulse amplitude still increased, presumably as a result of the increased negative feedback action of sex steroids. Simultaneous LH/FSH pulses developed during the night at onset of puberty but during the day only towards the end of pubertal development. The use of these novel highly sensitive IRMA methods demonstrated nocturnal LH and both diurnal and nocturnal FSH pulsatility to be present in older prepubertal boys. The early detectable FSH level plus the existence of solitary FSH pulses throughout puberty as well as in adult men support the hypothesis of the existence of a GnRH-independent FSH secretion in men. Our results are in accordance with the following hypotheses: (1) puberty is brought about by GnRH secretion increasing with time, both in frequency and amplitude, and first appearing during the night. (2) GnRH secretion decreases in frequency at the end of puberty due to the development of a negative feedback action by a testicular factor or factors. (3) FSH secretion in puberty is only partly dependent on GnRH secretion.