Four normal and one obese adult male subjects were exposed to hot air (48 C) for 1 hr after an overnight fast. Body temperature was elevated over 37.5 C and severe hyperhidrosis(hydrosis) with tachycardia occurred during the exposure. Body weight decreased by 0.5–1.5 kg in all subjects. In four of the subjects with normal body weight, plasma growth hormone (HGH) levels increased from less than 1.6 ng/ml to peaks ranging 6.2–30 ng/ml at 60 min after the beginning of heat exposure. HGH levels decreased to initial values within 1 hr after heat exposure was discontinued. In one subject, 21% overweight, although body temperature increased to 37.5 C, HGH levels showed an increment of only 1.5 ng/ml. Nonesterified fatty acids (NEFA) increased to peaks ranging 138.9–189.5% of initial values in four subjects during the exposure to heat, but varied little in one. No significant changes in values of cortisol, total thyroxineiodine, blood glucose, or hematocrit were noted during the heat exposure. The increased HGH response to hot air exposure did not occur in two subjects given oral administration of 100 g of glucose 0 and 30 min before heat exposure.
Source : http://press.endocrine.org