Changes in Growth Hormone Concentrations May Aid in Shifting Peripheral Fuel Utilization from Glucose and Amino Acids to Ketone Bodies and Fatty Acids

The fat mobilization-induced changes in hepatic metabolism are effective in conserving protein only because of changes that occur in glucose and amino acid utilization in peripheral tissues.

As ketone bodies, NEFAs, and VLDL triglycerides become the major energy supplies, there is less tissue demand for glucose or amino acids as energy substrates. Endocrine alterations, in addition to low insulin concentrations, may aid in promoting this switch in peripheral fuel utilization. In several species, growth hormone concentrations rise during a prolonged period of energy deprivation. Growth hormone is antagonistic to insulin, thus promoting an increase in the serum glucose concentration even in the presence of normal or near-normal serum insulin levels. In addition, growth hormone may have some direct effect on conserving protein and mobilizing lipid.

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