IMPAIRED GROWTH-HORMONE RESPONSES TO CIGARETTE-SMOKING IN OLDER SUBJECTS

The cardiovascular and hormonal responses to smoking of one cigarette (1.35 mg nicotine) were studied in 17 young (age range 19 to 24 years) and in 17 older (age range 50 to 74 years) subjects. Cortisol, prolactin (PRL), growth hormone (GH) and thyrotropin (TSH) were measured in plasma samples taken at 0, 15, and 30 min from smoking. Blood pressure increases were similar in the two groups, while heart rate increases were higher in the young subjects. Cortisol and PRL did not show any significant changes in either group. Small but significant decreases in TSH were observed In both groups, while GH increased significantly in the group of young subjects but not in the group of older subjects. Repeated measures analysis of variance revealed a significant difference in the GH responses, 15 min from smoking (p = 0.03). Since in the release of GH, participate, among others, central cholinergic mechanisms, the impairment of GH release to cigarette smoking indicates a diminished responsiveness of nicotinic receptors in the central nervous system in older subjects.