Nutritional effects on thyroid and catecholamine metabolism.

Adaptation to a change in energy intake is fundamental to survival and in prolonged semi-starvation energy expenditure can be halved (Keys, Brozek, Henschel, Mickelson & Taylor, 1950). Similarly, overfeeding normal young men induces a marked alteration in metabolism, a weight gain of only 10-1596 being accompanied by a 70% increase in energy expenditure (Sims, Danforth, Horton, Bray, Glennon & Salans, 1973). Thus man has adaptive mechanisms which generate large changes in energy output, and this seems to involve two major thermogenic hormones, thyroid and catecholamines. The thyroidal changes in response to starvation will be considered first.