Figure 7. Schematic representation of the effects of the modulation of THs levels in healthspan and lifespan in mice. Mice unable to synthesize THs exhibit growth retardation and periweaning death. Mice exhibiting a mild reduction on circulating THs levels develop obesity, glucose metabolism dysregulations and increased incidence of liver cancers, which compromise their quality of life. Mice exhibiting increased levels of THs exhibit reduced body weight and reduced glycaemia at fasting. However, these mice develop toxicity and exhibit a short lifespan. Interventions based on the modulation of THs reduce healthspan and/or lifespan in mammals.