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The relationship between endogenous testosterone and gonadotrophin secretion
N A Bridges1, P C Hindmarsh, P J Pringle
1International Growth Research Centre, Middlesex Hospital, London, UK.
Clinical Endocrinology
|April 1, 1993
Summary
This study reveals that follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are co-secreted, with testosterone pulses following LH pulses by 60 minutes. Daily testosterone level fluctuations alter LH pulse frequency, indicating rapid feedback at the hypothalamic level.
Area of Science:
- Endocrinology
- Reproductive Physiology
- Chronobiology
Background:
- The secretion patterns of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone in adult males are complex.
- Understanding the interplay and temporal relationships between these hormones is crucial for reproductive health.
Purpose of the Study:
- To investigate the 48-hour secretion profiles of LH, FSH, and testosterone in adult males.
- To examine the influence of endogenous circadian variations in testosterone on LH pulsatility.
- To determine the temporal relationships and pulse frequencies of LH, FSH, and testosterone.
Main Methods:
- Collected hormone profiles via 20-minute sampling over 48 hours in six healthy adult males (aged 21-23).
- Measured LH and FSH using immunoradiometric assay and testosterone via solid-phase radioimmunoassay.
- Utilized cross-correlation and spectral analysis (Fourier transformation) to analyze hormone pulsatility and temporal relationships.
Main Results:
- All three hormones exhibited pulsatile secretion with a circadian rhythm, peaking between 0200 and 0600 hours.
- Significant positive correlation found between LH and FSH pulses with no time lag (r=0.5, P=0.001).
- Testosterone pulses followed LH pulses by an average of 60 minutes (r=0.26, P=0.001).
- Dominant pulsatility periods were 200 minutes for LH/FSH and 400 minutes for testosterone.
- LH pulse frequency varied with testosterone levels: 180 minutes during high testosterone and 120 minutes during low testosterone (P<0.025).
Conclusions:
- FSH and LH are co-secreted, and testosterone release is closely timed after LH pulses.
- Circadian variations in serum testosterone concentration directly impact LH pulse frequency.
- Testosterone exerts a rapid feedback effect on the hypothalamic regulation of gonadotropin secretion.