The effect of thyrotropin releasing hormone (TRH) on levels of serum thyroid stimulating hormone (TSH), luteinizing hormone (LH) and follicle stimulating hormone (FSH) in female rats.

Abstract

The patterns of TSH, LH and FSH levels after TRH injection were studied in female rats in order to know if TRH induces the release of gonadotropin concurrently with TSH. TRH were subcutaneously injected to immature (2729 days of age, 6080 g b. w.) and adult (180250 g b. w. in the late diestrus state with the correct 4 days cycle) female rats of Wistar strain at the different dose as shown in Table 13. Three to 5 animals consist of each group.
Rats were killed by bleeding at different times (Tables 13) after injection, and serum levels of TSH, LH and FSH were measured by radioimmunoassay.
TSH release was evoked 5 min after injection of more than 2 μg TRH in immature rats. In adults, TSH release was shown 30 min after injection of 0.2 and 2 μg TRH and 5 min after injection of more than 20 μg TRH.
The time of recovery of TSH levels to 0 min had some relation with TRH dose in both female groups.
LH and FSH levels were not affected by TRH treatment.
It is concluded that higher blood TSH levels are not necessarily followed by higher gonadotropin levels although UMEZU et al.⁹⁾ observed higher LH levels with elevated TSH in immature female hypothyroid rats.
The authors acknowledge the gift of rat TSH, LH and FSH radioimmunoassay materials from the Rat Pituitary Hormone Distribution Program of the National Institute of Arthritis, Metabolism and Digestive Diseases.