Meeting Abstract
P3.130 Jan. 6 The effects of fasting and refeeding on plasma thyroid hormones (T4 and T3) in the green iguana, Iguana iguana KOHEL, K.A.; BRODERICK, C.E.*; Alfred University; Alfred University kohel@alfred.edu
Food intake plays an important role in the regulation of thyroid function in vertebrates, including ectotherms (Eales, 1988). Most studies on ectotherms on the control of thyroid function by nutrient intake were performed on teleost fish. Fasting resulted in decreased thyroid hormones (Milne et al., 1979; Flood and Eales, 1983), and refeeding resulted in increased thyroidal secretion of T4 and peripheral conversion to T3 (Higgs and Eales, 1977; Flood and Eales, 1983; MacKenzie et al., 1993). In the desert tortoise, thyroid hormones decreased significantly with chronic fasting (2 weeks) and increased significantly over 36 hours with increased nutrient intake (Kohel et al., 2001). To investigate thyroidal regulation in an ectotherm, the green iguana, 11 juvenile iguanas were kept in a 12h L: 12h D photoperiod, temperature ranging from 80-85�F, and fed daily. After 20 days of acclimation, the iguanas were fasted for 10 days and then refed. To measure the effects of fasting and refeeding on thyroidal regulation, plasma T4 and T3 levels were measured using T4 and T3 enzyme immunoassays at the beginning of the experiment, during fasting, after fasting, and for two consecutive days after refeeding. It was predicted that thyroid hormone levels would decrease with fasting and increase with refeeding.
