Human pancreatic tumor GH-releasing factor

Cortisol levels decrease after acute tobacco abstinence in regular smokers

OBJECTIVE

The aim of this study was to examine the effect of acute tobacco abstinence on cortisol levels in regular smokers, and whether abstinence-induced changes in cortisol levels are correlated with various signs and symptoms of the tobacco withdrawal syndrome.

METHODS

Smokers (N = 77, ≥15 cigarettes/day) attended two counterbalanced sessions (avg = 1 h), one following 12-20 h of abstinence and the other following ad lib smoking. At both sessions, salivary cortisol levels were measured at three time points. Additionally, a battery of self-report questionnaires, physiological assessments, and cognitive performance tasks were administered to measure signs and symptoms of tobacco withdrawal.

RESULTS

Salivary cortisol levels were significantly lower during the abstinent session versus the non-abstinent session. No significant associations were found between abstinence-induced changes in cortisol and other tobacco withdrawal measures, although there was suggestive evidence that abstinence-induced changes in cortisol levels and hunger were inversely associated to a modest degree.

CONCLUSION

Acute tobacco abstinence was associated with decreased cortisol levels. Cortisol dampening during acute tobacco abstinence may reflect nicotine-mediated modulation of hypothalamic-pituitary-adrenal axis activity, which may be relevant to the maintenance of tobacco dependence. Tobacco-withdrawal cortisol changes do not appear to be a cause or consequence of many manifestations of acute tobacco withdrawal with the possible exception of hunger.

Growth hormone neurosecretory dysfunction

The basis for understanding clinical disorders in the neuroregulation of GH secretion is derived from the complexity of the CNS-hypothalamic-pituitary axis. Studies in animals and humans demonstrate an anatomic, physiological and pharmacological evidence for neurosecretory control over GH secretion including neurohormones (GRH, somatostatin), neurotransmitters (dopaminergic, adrenergic, cholinergic, serotonergic, histaminergic, GABAergic), and neuropeptides (gut hormones, opioids, CRH, TRH, etc). The observation of a defect in the neuroregulatory control of GH secretion in CNS-irradiated humans and animals led to the hypothesis of a disorder in neurosecretion, GHND, as a cause for short stature. We speculate that in this heterogeneous group of children a disruption in the neurotransmitter-neurohormonal functional pathway could modify secretion ultimately expressed as poor growth velocity and short stature.