Prolactin Response to Thyrotropin-Releasing Hormone in Normal Subjects

Abstract

Synthetic thyrotropin releasing hormone (TRH) was administered intravenously to normal human subjects and the serum prolactin (PRL) response was measured. The effects of dose and of age and sex of the recipients on the PRL response were evaluated. The maximum increase in scrum PRL above the baseline level (max APRL) was used as the index of response. The max APRL increased linearly as a function of the log of the TRH dose between 6.25 and 100 μg of TRH, but did not increase further in response to 400 and 800 μg of TRH. Mean PRL responses did not vary with age in subjects of the same sex, but individual variability was greater in the older subjects of both sexes. PRL responses in each of 3 age groups of females, 20-39, 40-59 and 60-79 years old, were nearly double the responses observed in males of the same age groups (58.9 ± 4.7 ng/ml in all females vs 28.7 ± 2.4 ng/ml in all males, mean ± sem). In order to avoid diagnostic error in evaluating PRL response to TRH, criteria must be employed that are specific for TRH dose and for age and sex.