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© Georg Thieme Verlag, Stuttgart · New York
Time-Dependent Effects of Oral Thyrotropin-Releasing Hormone in Hyperthyroid Female Rats
14 March 2008 (online)
We have studied the thyrotropin (TSH) and thyroid hormone (T3) response to acute thyrotropin-releasing hormone (TRH) administration in rats previously rendered hyperthyroid by daily ip injection of 25 μg L-T4/100 g bw for 30 days. Animals were thereafter put on distilled water or TRH (2 mg/10 ml) as drinking solution for another 18 days, continuing T4 administration. On days 3 and 10 on oral TRH, the serum TSH and T3 response to TRH was studied by administering 2 μg of the tripeptide iv.
After 3 days, neither the animals on oral DW, nor those on oral TRH showed any response. Nevertheless, after 10 days, animals on oral TRH had a measurable, significant thyrotropin response. At sacrifice (18 days), animals on oral TRH had increased pituitary TSH content. These results confirm and extend a recent report from our laboratory (Iglesias, Llobera and Montoya 1985). We conclude that TRH-mediated thyrotropin accumulation in pituitary is the primary cause for the presence of this response.
TSH - Oral TRH - T 4 - T 3