Measurement of thyroid secretion rate of individual pigeons

¹ Department of Dairy Husbandry, University of Missouri, Columbia, Missouri

A method is described in which, by the use of radioiodine techniques, thyroid function of unanaesthetized pigeons was studied. Maximum accumulation of I¹³¹ in the pigeon thyroid was accomplished within 24 hours or less followed by rapid thyroidal-I¹³¹ release. (Average biological half-life of 2.73 ± .3 days.) Estimation of thyroid secretion rate (TSR) was then made for each pigeon by injecting graded doses of l-thyroxine until the level was reached which suppressed thyrotropic hormone secretion and thus prevented further thyroidal-I¹³¹ output. Individual TSR ranged from 1.0–2.5 µg/100 gm/day with an average for 35 adult common pigeons of 1.94 ± .07 µg/100 gm/day l-thyroxine. Analyses of correlation coefficients indicated a significant negative correlation existed between TSR and biological half-life of thyroidal-I¹³¹. Nonsignificant correlations existed between TSR and 24-hour I¹³¹ uptake and between TSR and body weight. The level of thyroid hormone secretion did not influence the pigeons' crop-sac response to standard lactogenic hormone.