The role of hyperphagia and hypothyroidism in the development of the obese-hyperglycemic syndrome in mice (ob/ob).

Obese-hyperglycemic mice show hyperphagia and hypothyroidism. The reduced body temperature can be normalized by injection of thyroxin. Limiting food intake to normal non-obese levels reduces blood sugar level, insulin content of the blood and body weight. However, reduction of all these parameters together until normal level occurs only when combining thyroxin injection with restricted diet. Weight of epididymal fat pad, nuclear volume of Leydig cells and volumes of islets of Langerhans normalize too during the combined treatment. It is argued that in adult obese mice hyperphagia and hypothyroidism are two separate factors which cannot be completely compensated for one by another. At least some symptoms in the obese-hyperglycemic syndrome could be attributed to hypothalamic disturbances caused by a reduced thyroidal activity at a very early age after birth.