Plasma concentration of luteinizing hormone, testosterone, dehydroepiandrosterone, androstenedione between birth and one year in the male dog: longitudinal study and hCG stimulation.

Abstract

A longitudinal study from peripheral blood, with samples collected every week, was performed between birth and one year of age on young Fox terriers dogs in order to determine the patterns of plasma LH, T, DHA and A concentrations. T, DHA, A curves show the same profile. The dog model shows the 3 successive steps preceding the adult life that are met in one year time: First, an infantile period between birth and the 12th week of age: the basal level of LH (4.29 ng/ml) and the 3 androgens levels (T less than 0.3 ng/ml, DHA less than 0.45 ng/ml, A less than 0.36 ng/ml) are low. A pubertal period, between the 13th week and the 36th week of age: we observe the maximum activity of the pituitary gland. The basal level of LH (7.97 ng/ml) significantly increase (P less than 0.001). The mean levels of androgens from 17 to 27 weeks of age are still quite low although significantly higher (P less than 0.03) for T and DHA than previously. After the 27th week of age, the androgens concentrations drastically increase. A post pubertal period begins at the 36th week of age. The mean LH (5.85 nh/ml) decrease. The androgens concentrations seem to plateau during the 12th month of age in the range of 2.5-5 ng/ml for T, 1.5-2.5 ng/ml for DHA and 1-2 ng/ml for A. hCG test (35 UI/kg, IM), with samples collected at 6, 12, 24, 30, 36 and 48 hours post injection, were performed at 1, 4, 7, 9 and 12 months of age. At 1 month, only minor variations were noticed; but after 4 months of age, for the 3 steroids, the same time course response was observed as in the adult dog: maximum levels were reached earlier for DHA (6-12 h) than for T and A (24 h).