Secretory profiles of LH and testosterone in pubescent male goat kids

Abstract

Secretory profiles of peripheral plasma luteinising hormone (LH) and testosterone (T) in pubescent male goat kids were determined in serial blood samples collected at 15 min intervals for a 6 h period fortnightly over a 4 month period by radioimmunoassays. In four kids, after remaining at a high level at 12–15 weeks of age, the baseline concentration of LH declined until 20–21 weeks, when it increased to a maximum value. Similarly, after a maximum value of 5.21 ng ml −1 at 12–13 weeks of age, the mean LH concentration decreased, with another increase at 20–21 weeks of age. The maximum pulse frequency was observed at 12–13 weeks of age. After lower values at 14–19 weeks of age, it increased at 20–21 weeks of age. Likewise, the pulse magnitude was highest at 12–13 weeks of age and decreased with advancing age. In two kids, the baseline T concentration was 0.35 ng ml −1 at 12 weeks of age, and had increased to a mean of 2.01 ng ml −1 at 20 weeks. The mean T concentration at 12–16 weeks of age ranged between 1.20 and 1.24 ng ml −1 and increased at 20 weeks, reaching a peak value at 26 weeks of age. After relatively higher values at 12 weeks of age, the pulse frequency remained low between 14 and 18 weeks of age and increased thereafter. The pulse magnitude at 12 weeks of age was 3.60 ng ml −1, it fluctuated between 14 and 18 weeks and then increased consistently to reach the highest value of 7.18 ng ml −1 at 26 weeks of age. It appears that an increase in LH mean concentration, and pulse magnitude and frequency around 12 weeks of age stimulated testicular growth and induced spermatogenesis in pubescent goat kids.