Effect of food deprivation on baseline iodothyronine and cortisol concentrations in healthy, adult horses.
Six healthy, adult horses, with normal (mean +/- SEM) baseline serum concentrations of total triiodothyronine (T3, 1.02 +/- 0.16 nmol/L), free T3 (FT3, 2.05 +/- 0.33 pmol/L), total thyroxine (T4, 19.87 +/- 1.74 nmol/L), free T4 (FT4, 11.55 +/- 0.70 pmol/L), total reverse T3 (rT3, 0.68 +/- 0.06 nmol/L), and cortisol (152.75 +/- 17.50 nmol/L), were judged to be euthyroid on the basis of response to a standardized thyroid-stimulating hormone response test. Serum concentrations of T3, FT3, T4, FT4, rT3, and cortisol were determined immediately before and every 24 hours during a 4-day period of food deprivation, when water was available ad libitum. Similar variables were measured 72 hours after refeeding. Decreases (to percentage of baseline, prefood deprivation value) in circulating T3 (42%), T4 (38%), FT3 (30%), and FT4 (24%) concentrations were maximal after 2, 4, 2, and 4 days of food deprivation, respectively (P < 0.05). Increases (compared with baseline, prefood deprivation value) in rT3 (31%) and cortisol (41%) concentrations were maximal after 1 and 2 days of food deprivation, respectively (P < 0.05). Refeeding resulted in increase in serum T4 and FT4, and decrease in rT3 and cortisol concentrations toward baseline values, after 72 hours (P < 0.05). Refeeding did not effect a return of T3 or FT3 concentration to baseline values after 72 hours (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Messer
N T
NT
Department of Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia.
Johnson
P J
PJ
Refsal
K R
KR
Nachreiner
R F
RF
Ganjam
V K
VK
Krause
G F
GF
D000704:Analysis of Variance; D000818:Animals; D005260:Female; D005508:Food Deprivation / Q000502:physiology*; D006736:Horses / Q000097:blood*; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D011863:Radioimmunoassay / Q000662:veterinary; D013963:Thyroid Hormones / Q000097:blood*; D013997:Time Factors
D013963:Thyroid Hormones; D006854:Hydrocortisone