Looking for the Mechanism of Action of Thyroid Hormone

Table 2

Morphological and biochemical responses to thyroid hormone during amphibian metamorphosis.

Tissue	Response
	Morphological	Biochemical
Brain	Restructuring, axon guidance, axon growth, cell proliferation, and death	Cell division, apoptosis, and new protein synthesis
Liver	Restructuring, functional differentiation	Induction of urea cycle enzymes and albumin; larval to adult haemoglobin gene switching
Eye	Repositioning; new retinal neurones and connections; lens structure	Visual pigment transformation (porphyropsin → rhodopsin); 𝛽- crystallin induction
Skin	Restructuring; skin granular gland formation; keratinization and hardening; apoptosis	Induction of collagen, 63 kDa (adult) keratin and magainin; induction of collagenase
Limb bud, lung	Do novo formation of bone, skin, muscle, nerves, and so forth.	Cell proliferation and differentiation; chondrogenesis
Tail, gills	Complete regression	Programmed cell death induction and activation of lytic enzymes (collagenase, nucleases, phosphatases, and matrix metalloproteinases); lysosome proliferation
Pancreas, Intestine	Major tissue restructuring	Reprogramming of phenotype, induction of proteases, fatty acid binding protein, and stromelysin-3
Immune system	Redistribution of cell populations	Altered immune system and appearance of new immunocompetent components
Muscle	Growth and differentiation; apoptosis	Induction of myosin heavy chain

See [11, 34] for details.