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Assessment of dose and time responses to TRH and thyrotropin in healthy dogs
Author(s) -
Sparkes A. H.,
GruffyddJones T. J.,
Wotton P. R.,
Gleadhill A.,
Evans H.,
Walker M. J.
Publication year - 1995
Publication title -
journal of small animal practice
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.7
H-Index - 67
eISSN - 1748-5827
pISSN - 0022-4510
DOI - 10.1111/j.1748-5827.1995.tb02907.x
Subject(s) - medicine , thyrotropin releasing hormone , endocrinology , physiology , hormone
Changes in total thyroxine (T 4 [TT 4 ]), free T 4 (FT 4 ) and total tri‐iodothyronine (T 3 [TT 3 ]) in serum after the intravenous administration of different doses of thyrotropin (TSH) and thy‐rotropin‐releasing hormone (TRH) were measured in six healthy beagles. Significant (P<0·05) elevations in serum TT 4 , FT 4 and TT 3 were observed at each sampling time (two, four, five, six, seven, eight and 10 hours) after administration of 1, 3 or 5 iu (total dose) TSH and peak mean responses were observed six to eight hours after injection. At six hours after injection the mean TT 4 , FT 4 and TT 3 levels were approximately 2·6, 3·9 and 1·5 times basal levels, respectively, and there were no significant differences between the three doses of TSH. Significant (P<0·05) elevations in serum TT 4 and FT 4 but not TT 3 were observed at each sampling time (two, four, five, six, seven and eight hours) after the administration of TRH. Peak mean responses were observed at four hours after injection at which time TT 4 and FT 4 levels were approximately 1·7 and 1·9 times basal levels, respectively. No significant differences were observed between the four doses of TRH used (100, 200, 300 and 600 μg total dose). Concentrations of TT 4 , FT 4 and TT 3 were significantly (P<0·05) higher following the administration of TSH compared with TRH, and the response to TRH showed greater individual variation.