Data from: Mitochondrial function is enhanced by thyroid hormones during zebra finch development

An organism's response to its environment is largely underpinned by changes in the energy supplied by the aerobic mitochondrial metabolism via adenosine-tri-phosphate (ATP) production. ATP is especially important under energy-demanding conditions, such as during growth. The biological mechanisms through which environmental factors feed-back on mitochondrial function, and thus growth, are poorly understood, but recent studies suggest a role of hormones. In particular, thyroid hormones (THs) are key regulators of growth and metabolism in vertebrates, which react flexibly to environmental influences, such as temperature or nutrient availability. We manipulated TH levels within physiological ranges during the main growth phase in zebra finch (Taeniopygia guttata) nestlings, to test for causal relationships with mitochondrial function and growth. Our TH-treatment accelerated skeletal growth and maximal mitochondrial working capacity, ETS – a mitochondrial trait reflecting ATP production potential. Furthermore, TH marginally elevated cellular metabolic rate and oxidative phosphorylation, the final step of ATP production. To our knowledge, this is the first study to characterize the regulation of mitochondria by TH during development in a naturalistic context and to address the implications for fitness.