Relationship of age to seasonal levels of LH, FSH, prolactin and testosterone in male, white-tailed deer.

Seasonal levels of LH, FSH, Prolactin (PRL) and testosterone (T) were determined in blood plasma of penned male white-tailed deer, ranging in age from 2 to 10 yr. Peak levels of T (observed around the rutting season in November) gradually increased until the 7th yr and then they began to decline slowly; a sharp decrease was registered in the 10th yr. Peak levels of PRL (measured in June) steadily increased until the 6th yr and then dropped rapidly in the 8-9-yr-old group. Peak concentrations of FSH (observed during September-October) rose gradually until the 6th yr, decreased in 8-yr-olds and then increased again in the 9th and 10th yr of life. On the other hand LH maxima (occurring during July-September) were rising until the 4th yr and then remained steady until the 6th yr. LH peaks in the 8th and 9th yr were more than 50% higher than that of the 4-6th yr. These data indicate that increasing peak levels coincide with approaching "prime male age" around 5-7 yr. In senior bucks (9-10 yr) decreasing gonadal function may be the sign of diminished responsiveness to pituitary hormones since gonadotrophins are elevated to the "castrate-type" levels.