Immunoreactive GnRH and TRH in the peripheral blood of ovariectomized and ovariectomized-thyroidectomized rats:...

Immunoreactive gonadotropin-releasing hormone (IR-GnRH) and thyrotropin-releasing hormone (IR-TRH), luteinizing hormone (LH), thyrotropin (TSH), and prolactin (PRL) in the peripheral sera of proestrus, estrus, diestrus as well as long term ovariectomized (Ovx) and ovariectomized-thyroidectomized (Ovx-Tx) rats were measured by radioimmunoassay. Ovx and Ovx-Tx rats were decapitated on days 50, 70, and 90 following operation. The concentration of serum IR-GnRH in Ovx and Ovx-Tx rats on days 50 and 70 post-ovariectomy was lower than that in intact females. Serum IR-GnRH level in rats 90 days post-ovariectomy was increased by 2- to 4-fold as compared with intact rats. The concentration of serum IR-TRH was gradually increased in Ovx and Ovx-Tx rats from day 50 to day 90 post-ovariectomy. Thyroidectomy did not alter the concentration of serum IR-GnRH and IR-TRH in Ovx rats on days 70 and 90 post-ovariectomy. Thyroidectomy increased serum LH and TSH levels but reduced serum PRL level in Ovx rats. There is no correlation between serum IR-GnRH and LH levels as well as serum IR-TRH and TSH or PRL levels, respectively, in chronic Ovx and Ovx-Tx rats.