Influence of thyrotropin-releasing hormone on autonomic nervous system determined by the variations in R-R interval on electrocardiogram.

The change of variation in R-R interval on electrocardiograms (CVq) was examined in healthy subjects and patients with Graves' disease before and after an intravenous administration of 500 micrograms of Thyrotropin-releasing hormone (TRH). CVq was significantly elevated after TRH stimulation and returned to the control level within 120 min. This phenomenon was found not only in healthy subjects but also in patients with untreated Graves' disease whose levels of CVq were lower than in normal subjects. Pretreatment with atropine inhibited the response of CVq to TRH. These data suggest that TRH has a stimulatory effect on the parasympathetic nervous system, determined by the variations in R-R interval.