Jennifer D. Wallace

Altered endogenous growth hormone secretory kinetics and diurnal GH-binding protein profiles in adults with chronic liver disease

OBJECTIVE Increased serum GH concentrations and GH responses to a variety of stimuli have been reported in patients with chronic liver disease (CLD). We Investigated the pulsatile pattern of endogenous GH release and GH‐binding protein (GHBP) and insulin‐like growth factor‐I (IGF‐I) diurnal profiles in adults with cirrhosis, in comparison with healthy, matched control subjects.

The hormonal response of older men to sub-maximum aerobic exercise: The effect of training and detraining

The hormonal response of 32 older men (70-80years) to a bout of sub-maximum aerobic exercise was examined before, after 16weeks of resistance or aerobic training and again after 4weeks of detraining. Blood samples were obtained at rest and immediately post sub-maximum exercise (30min @ 70% VO(2) max) to determine the concentrations of growth hormone (GH), insulin-like growth factor-1 (IGF-1), testosterone (Test), sex hormone-binding globulin (SHBG) and the calculation of free testosterone (FT). Both training groups had significant increases in leg strength and VO(2) max after 16weeks training but leg strength and VO(2) max returned to pre-training levels in the aerobic training and resistance training groups, respectively. During the 20week study there was no change in resting concentrations of any hormones among the three groups. There was no increase in GH, IGF-1 or SHBG immediately post sub-maximum exercise in any of the groups before training, after 16weeks training or after 4weeks detraining. Testosterone and FT increased immediately post sub-maximum exercise within all groups before training, after 16weeks training and after 4weeks detraining with the increase in Test and FT higher after 16weeks of resistance training compared to before training and after 4weeks detraining within the resistance training group. The increased responsiveness of Test and FT after 16weeks of resistance training was lost after 4weeks of detraining. Our results indicate that some physiological and hormonal adaptations gained after 16weeks training are lost after only 4weeks detraining.

Growth hormone abuse in athletes: A review

Growth hormone (GH) is being used by elite athletes to enhance performance. The rationale appears to come from studies in adults with GH deficiency, where GH replacement has been shown to alter body composition so that lean tis sue mass is increased and fat mass is decreased, to enhance aerobic and resistance performance, to increase cardiac output, to enhance thermal adaptation during exertion, to increase collagen syn thesis, and to modify intermediary metabolism. Documentation of enhanced performance in athletes, however, is currently lacking. Detection of exogenous GH abuse presents a number of unique problems, in that endogenous GH is secreted in a pulsatile fashion and is stimulated by acute exercise. Also, recombinant 22 kDa GH is currently indistinguishable from the endogenous hormone. An international collaborative study group has been established to develop a means of differentiating supra-physiological doses of exogenous GH from endogenous GH secretion in athletes. Current testing strategies center around markers of GH action (the insulin-like growth factor system and markers of bone and collagen turnover), and molecular isoforms of GH. Although additional validation work is required, a test to detect GH abusers can be implemented in the near future.

Skeletal and Cardiac Muscle in Adults with Growth Hormone Deficiency

The early descriptions of the physical capacities of adults with Growth Hormone (GH) deficiency (GHD) appeared in the late 1980s and early 1990s, highlighting reductions in skeletal muscle mass and force generation, aerobic exercise capacity, and cardiac muscle mass and function. This review will attempt to highlight recent understandings of the mechanisms underlying these abnormalities and the results of GH replacement therapy.