Dr. Goodyear

Insulin and Prolactin inhibit liver SHBG production.  Testosterone, Estradiol and T4 stimulate SHBG in in vitro study.

Though, studies have shown that resistance training increases Testosterone production, this study finds that artificial suppression of Testosterone reduced myogenic response to 8 weeks of resistance training.

Study looked at the threshold of symptoms of hypogonadism in men < 40 based on serum Testosterone levels.  The study found the prominent symptom was fatigue and the cut off Total Testosterone level was < 400 ng/dl.

Exercise is not just for calories out.  Exercise increases growth hormone, IGF-1, glucagon-like peptide 1, IL-6, and IL-1ra.  The effect is to GH increases beta islet cell mass and protects beta cell lines against IL-1beta, Interferon-gamma and TNF-alhpa induced apoptosis.  IL-6 increased production increases GLP-1 and IL-1ra which counters IL-1beta.  Interleukin-1beta induces islet cell apoptosis and thus IL-1ra counters this pro-inflammatory signal.

The opposite effect strikes again: elevated free androgen index is associated with CV risk in perimenopause women across 5 ethnic groups.  Low SHBG was associated with increased CVD.

Low Testosterone associated with increased leptin independent of BMI.  Increased leptin, low T, and SHBG were associated with increasing BMI in men.  Excluding BMI points to a more cause-effect relationship between elevated leptin and low T in men.

Low Testosterone in men correlates with increasing BMI and increasing leptin in men.

Study of hypogonadal men with low T and elevated leptin levels finds that Testosterone therapy reduced leptin levels.

Increasing leptin levels in women with/without PCOS correlate positively with serum Testosterone levels.

Testosterone therapy in obese men with type II Diabetes and low T improved weight,  lipids, HgbA1c, and blood pressure.  There was more improvement with Leptin than with diet/exercise alone. What is very important is that the control group (diet, exercise, DM meds) had improvement in Testosterone levels, HgbA1c, lipids, BMI, and blood pressure; just not as strong as the treatment arm with Testosterone.

great review of adiposity versus satiety signals and the hypothalamus signaling.

orexigenic versus anorexigenic signaling and control of appetite at the level of the hypothalamus.

Good review of Orexins.

Three month study of men with low T, found that Testosterone therapy improved insulin sensitivity and reduced leptin levels.  The group of men here were described as "healthy, non-obese men".   Remember, low T is a biomarker of poor health in men, so the authors statement about the study group is inaccurate.  This also points to a relatively quick metabolic effect by Testosterone and a direct effect on insulin receptor effect and adipocyte leptin release.

Study of infertile, obese men found negative correlation between leptin and Testosterone.

mouse study finds that increased oxidative stress and high leptin levels in obese mice led to decreased sperm count, decreased sperm motility, and low T.

Salivary CRP correlates with serum CRP in adolescents with inflammation.

Exciting: salivary CRP found to correlate with serum CRP.

serum and salivary oxidative stress biomarkers used to follow children with autism in Iraq.

Study of Iraqi population at elevated risk of stroke found that both serum and salivary levels of malondialdehyde, glutathione, superoxide dismutase, and uric acid proved useful as potential biomarkers of risk assessment.