Growth hormone response to intravenous diazepam and placebo in 82 healthy men

Modulation of the growth hormone-insulin-like growth factor (GH-IGF) axis by pharmaceutical, nutraceutical and environmental xenobiotics: an emerging role for xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. A review

The growth hormone-insulin-like growth factor (GH-IGF) axis has gained considerable focus over recent years. One cause of this increased interest is due to a correlation of age-related decline in plasma GH/IGF levels with age-related degenerative processes, and it has led to the prescribing of GH replacement therapy by some practitioners. On the other hand, however, research has also focused on the pro-carcinogenic effects of high GH-IGF levels, providing strong impetus for finding regimes that reduce its activity. Whereas the effects of GH/IGF activity on the action of xenobiotic-metabolizing enzyme systems is reasonably well appreciated, the effects of xenobiotic exposure on the GH-IGF axis has not received substantial review. Relevant xenobiotics are derived from pharmaceutical, nutraceutical and environmental exposure, and many of the mechanisms involved are highly complex in nature, not easily predictable from existing in vitro tests and do not always predict well from in vivo animal models. After a review of the human and animal in vivo and in vitro literature, a framework for considering the different levels of direct and indirect modulation by xenobiotics is developed herein, and areas that still require further investigation are highlighted, i.e. the actions of common endocrine disruptors such as pesticides and phytoestrogens, as well as the role of xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. It is anticipated that a fuller appreciation of the existing human paradigms for GH-IGF axis modulation gained through this review may help explain some of the variation in levels of plasma IGF-1 and its binding proteins in the population, aid in the prescription of particular dietary regimens to certain individuals such as those with particular medical conditions, guide the direction of long-term drug/nutraceutical safety trials, and stimulate ideas for future research. It also serves to warn athletes that using compounds touted as performance enhancing because they promote short-term GH release could in fact be detrimental to performance in the long-run.

Benzodiazepines and anterior pituitary function

Benzodiazepines (BDZ) are one of the most prescribed classes of drugs because of their marked anxiolytic, anticonvulsant, muscle relaxant and hypnotic effects. The pharmacological actions of BDZ depend on the activation of 2 specific receptors. The central BDZ receptor, present in several areas of the central nervous system (CNS), is a component of the GABA-A receptor, the activation of which increases GABAergic neurotransmission and is followed by remarkable neuroendocrine effects. The peripheral benzodiazepine receptors (PBR), structurally and functionally different from the GABA-A receptor, have been shown in peripheral tissues but also in the CNS, in both neurones and glial cells, and in the pituitary gland. BDZ receptors bind to a family of natural peptides called endozepines, firstly isolated from neurons and glial cells in the brain and then in several peripheral tissues as well. Endozepines modulate several central and peripheral biological activities, including some neuroendocrine functions and synthetic BDZ are likely to mimic them, at least partially. BZD, especially alprazolam (AL), possess a clear inhibitory influence on the activity of the HPA axis in both animals and humans. This effect seems to be mediated at the hypothalamic and/or suprahypothalamic level via suppression of CRH. The strong negative influence of AL on hypothalamicpituitary-adrenal (HPA) axis agrees with its peculiar efficacy in the treatment of panic disorders and depression. BZD have also been shown to increase GH secretion via mechanisms mediated at the hypothalamic or supra-hypothalamic level, though a pituitary action cannot be ruled out. Besides the impact on HPA and somatotrope function, BDZ also significantly affect the secretion of other pituitary hormones, such as gonadotropins and PRL, probably acting through GABAergic mediation in the hypothalamus and/or in the pituitary gland. In all, BDZ are likely to represent a useful tool to investigate GABAergic activity and clarify its role in the neuroendocrine control of anterior pituitary function; their usefulness probably overrides what had been supposed before.

Dose-dependent effects of intravenous alprazolam on neuroendocrine, biochemical, cardiovascular, and behavioral parameters in humans

Neuroendocrine, biochemical, cardiovascular, and behavioral parameters were assessed in seven normal volunteers for 2 h after intravenous administration of alprazolam (APZ). Three doses of APZ (0.003, 0.007, and 0.02 mg/kg) were administered to each subject in a random order with at least 4 days between infusions. Plasma growth hormone and sedation increased in a dose dependent manner after APZ, and there was a dose dependent change in the shape of the cortisol response to APZ. No dose-response relationships were evident for plasma ACTH and norepinephrine. These differences in dose-response relationships may reflect the involvement of multiple systems in controlling neuroendocrine, biochemical, and subjective responses to APZ infusion. The optimal dose of APZ needed to produce a neuroendocrine or behavioral change appears to differ depending on the parameter of interest.

Effects of central and peripheral type benzodiazepine ligands on growth hormone and gonadotropin secretion in male rats

The action of central and peripheral type benzodiazepine ligands on growth hormone, luteinizing hormone and follicle stimulating hormone levels in serum were studied in male rats. Graded doses of Ro 5-4864, that binds to the peripheral type benzodiazepine receptors, clonazepam, a fairly pure central type agonist and diazepam, a mixed-type agonist, were given intraperitoneally. Also a benzodiazepine partial inverse agonist, FG 7142, was investigated. Clonazepam increased growth hormone levels at 0.2 mg/kg while higher doses were not active. Diazepam (5-25 mg/kg) was not effective. FG 7142 (15 mg/kg) and Ro 5-4864 (25 mg/kg) decreased growth hormone levels. Flumazenil, a central-type antagonist, reversed at least partially the effects of clonazepam and FG 7142, suggesting an effect through GABA-benzodiazepine complex. Elevation of growth hormone could be associated with anxiolysis and decrease of growth hormone with enhanced anxiety. Clonazepam (0.2-5 mg/kg) and diazepam (5-25 mg/kg) increased luteinizing hormone concentrations, but only the effects of 1 mg/kg of clonazepam and 5 mg/kg of diazepam reached statistical significance. Even FG 7142 caused a modest increase of luteinizing hormone at 5 mg/kg, but Ro 5-4864 rather decreased luteinizing hormone, although not significantly. Flumazenil (25 mg/kg) antagonized partially the effects of diazepam and clonazepam. Effects of Ro 5-4864 and FG 7142 were not modified by flumazenil or PK 11195, a peripheral-type mixed antagonist/agonist. Luteinizing hormone stimulation by benzodiazepine ligands may be a pituitary action while inhibition could be caused by the activation of the central GABAergic system. Serum follicle stimulating hormone levels were not significantly altered by central or peripheral type benzodiazepine agonists or antagonists.

Adrenocorticotropin hormone response to diazepam in healthy young men

The effects of diazepam (DZ) infusions on changes in adrenocorticotropin hormone (ACTH) are a source of debate. In this study, 66 healthy young adult men were evaluated for changes in plasma ACTH after intravenous infusions with placebo, 0.12 mg/kg and 0.20 mg/kg of DZ. After the higher DZ dose, 85% of the subjects demonstrated a decrease in ACTH of 20% or more, with the nadir occurring between 30 and 60 min postinfusion and values returning to baseline levels by 180 min. These results support the conclusion that at the clinically relevant doses used here, DZ infusions are associated with a significant decrease in ACTH.

Endocrine and receptor pharmacology of serotonergic anxiolytics, antipsychotics and antidepressants

Several classes of drugs that modify serotonin (5-HT) neurotransmission are either currently used, or are being evaluated for their potential use in the treatment of anxiety, schizophrenia, and depression. 5-HT1A agonists are considered potential anxiolytics, while some atypical antipsychotics are potent 5-HT2 antagonists (and also have modest dopamine D2 affinity). Furthermore, there is a diverse group of serotonergic drugs that may be effective antidepressants. Secretion of ACTH, corticosterone/cortisol, prolactin, renin, oxytocin and vasopressin are stimulated by activation of different 5-HT receptor subtypes, while other neurotransmitter receptors also influence the secretion of these hormones. We compared the receptor binding profiles of 5-HT anxiolytics, antipsychotics and antidepressants with their endocrine effects. These comparisons could aid in understanding both the therapeutic and side effects of these drugs.

Neuroendocrine effects of diazepam in panic and generalized anxiety disorders

The adrenocorticotropic hormone (ACTH), cortisol, and growth hormone responses to four consecutive, logarithmically increasing doses of intravenous diazepam compared with placebo given at 15-min intervals were examined in patients with panic disorder (n = 13), generalized anxiety disorder (n = 8), and healthy controls (n = 13). Diazepam caused dose-dependent decreases in cortisol and increases in GH and dose-independent decreases in ACTH. There were no patient-control differences, possibly due to either the small sample size of the experimental paradigm, which tested subjects in an upright, sitting position in mildly arousing circumstances.

Response of three hormones to diazepam challenge in sons of alcoholics and controls

This study evaluates the hypothesis that the decreased reaction to ethanol reported for sons of alcoholics will also be observed following infusions of a benzodiazepine. The investigation compared 37 men who were family history positive for alcoholism with 37 family history negative controls on postinfusion levels of cortisol, prolactin, and growth hormone following 0.12 and 0.20 mg/kg of diazepam given IV over 7 minutes. The results demonstrated no evidence of a decreased response for the sons of alcoholics on the levels of these three hormones.