[Reaction of the thyroid gland to a single and prolonged administration of prolactin]

A study was made of the thyroid and hypophysis response to the administration of a summary analogous dose of prolactin injected in a single dose or in the course of 5 days. Experiments were made on female rats at the diestrus stage. The content of thyroid hormones and thyrotropic hormone (TTH) in the blood was determined by radioimmunoassay. The concentration of thyroid hormones and TTH was compared in the basal state and 30, 60, 120 and 180 min after prolactin injection. An acute prolactin administration was shown to result in an elevated TTH level on the 30th minute and T4 on the 60th minute. Five-day hyperprolactinemia caused a decrease in the content of thyroid hormones in the blood and disturbed positive correlative interrelationships between the thyroid hormones and negative ones between thyroxine and TTH. It is assumed that the preservation of a high prolactin level in the blood can maintain the hyperthyroid state.