Effects of Tartrate Thyrotropin -Releasing Hormone Treatment on Serum Thyrotropin, Free Triiodothyronine, Free Thyroxine and Prolactin Levels in Patients with Spinocerebellar Degeneration

The aim of the present study was to investigate the pituitary-thyroid axis function during the long-term (30 days) intramuscular administration of 4 mg/day of thyrotropin-releasing hormone tartrate (TRH-T) in 15 patients with spinocerebellar degeneration. The study was performed as follows: (1) acute 4 mg TRH-T test with hourly prolactin (PRL) and thyroid-stimulating hormone (TSH) level evaluations for 6 h; (2) placebo; and (3) 4 mg/day of TRH-T administration for 30 days with TSH, PRL, and free T3 and T4 (FT3 and FT4) levels evaluated on days 1,15 and 30. Hormone determination was performed just before and 1 h after placebo or TRH-T administration. The acute administration of TRH-T caused a sustained rise of TSH which lasted until the 6th hour and of PRL which declined after 1 h (p 3 or FT4 was observed. On the 1st day of treatment, 1 h after the TRH-T injection, a significant increase of both TSH and PRL levels occurred (p 3 and FT4 was observed on the 15th day of treatment but not on the 30th day. In conclusion, the different patterns of TSH and PRL secretion during long-term TRH-T treatment can be explained taking into account the different effects of TRH on TSH and PRL pools, although down-regulation or desensitization of TRH receptors on thyrotrophs cannot be ruled out.