Effects of oral administration of anti-inflammatory doses of prednisone on thyroid hormone response to thyrotropin-releasing hormone and thyrotropin in clinically normal dogs.
Prednisone was given orally to 12 dogs daily for 35 days at an anti-inflammatory dosage (1.1 mg/kg of body weight in divided dose, q 12 h) to study its effect on thyroxine (T4) and triiodothyronine (T3) metabolism. Six of these dogs were surgically thyroidectomized (THX-Pred) and maintained in euthyroid status by daily SC injections of T4 to study peripheral metabolism while receiving prednisone; 6 dogs with intact thyroid gland (Pred) were given prednisone; and 6 additional dogs were given gelatin capsule vehicle as a control group (Ctrl). Baseline T4 concentration after 4 weeks of treatment was not significantly different in dogs of the THX-Pred or Pred group (mean +/- SEM, 2.58 +/- 0.28 or 3.38 +/- 0.58 micrograms/dl, respectively) vs dogs of the Ctrl group (2.12 +/- 0.30 micrograms/dl). A supranormal response of T4 to thyrotropin was observed in dogs of the Pred group, but the T4 response to thyrotropin-releasing hormone was normal. Baseline T3 concentration in dogs of both steroid-treated groups was significantly (P < 0.05) lower after 2 and 4 weeks of prednisone administration vs pretreatment values, but normalized 2 weeks after prednisone was stopped. Free T3 (FT3) and T4 (FT4) fractions and absolute FT3 and FT4 concentrations were not altered by prednisone administration. Reverse T3 (rT3) concentration in vehicle-treated Ctrl dogs (26.6 +/- 3.5 ng/dl) was not different from rT3 concentration in dogs of the THX-Pred (25.7 +/- 4.3 ng/dl) and Pred (28.9 +/- 3.8 ng/dl) groups after 4 weeks of medication.(ABSTRACT TRUNCATED AT 250 WORDS)
Moore
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GE
Department of Physiology, College of Veterinary Medicine, University of Georgia, Athens 30602.
Ferguson
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DC
Hoenig
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M
D000284:Administration, Oral; D000818:Animals; D004285:Dogs / Q000097:blood*; D008297:Male; D011241:Prednisone / Q000494:pharmacology*; D013972:Thyrotropin / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D013974:Thyroxine / Q000097:blood / Q000187:drug effects*; D014284:Triiodothyronine / Q000097:blood / Q000187:drug effects*; D014285:Triiodothyronine, Reverse / Q000097:blood / Q000187:drug effects
D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013974:Thyroxine; D011241:Prednisone