Dr. Goodyear

Testosterone inhibits CRH and thus cortisol.

Testosterone inhibits CRH and thus cortisol production in men.  This has implications in men with low T and low Cortisol.

Leptin does have inhibitory activity at the level at the HPA; in addition to the inhibition at the gonadal level.

Testosterone increases dopamine signaling.  This study was done on male rats.  No effect was seen with Estradiol.

vitamin D supplementation (2,000 IU) prolongs remission of Crohn's disease.  Of interesting note, the vitamin D group maintained gut integrity and had a decrease in gut permeability.

Only abstract available here, but low T is the result of primary (testicular failure) and/or secondary (HPA failure). 

no correlation between total Testosterone with LUTS and prostate size in men.

Resistance training increases Testosterone in younger and older men.  The effects in older men appears to involve more of a decreased metabolism.  

Leptin and Testosterone.  Interesting relationship that differs between the sexes.

high leptin levels found to inhibit pituitary LH/FSH release.  Of note, high leptin levels inhibited leydig cell production of Testosterone following hCG stimulation.  This is a rat in vitro study.

Leptin shown to inhibit steroid hormone synthesis in the gonads via inhibition of 17beta-HSD.  This is in addition to other reports of inhibition of 17,20 lyase, adrenal cortisol inhibition, inhibition of CRF, and inhibition of LH/FSH.

Leptin inhibits CRH, thus decreasing the HPA axis.

Leptin inhibits hormone production from the adrenal cortex, but increases catecholamine release from the adrenal medulla.

Kisspeptin increases LH pulse frequency and pluse amplititude; the result is an increase in Testosterone secretion.

Normal leptin levels are critical to puberty; but in obese men, increased leptin is associated with gonadal decrease in Testosterone.  It appears to occur through a decrease in 17-OH progesterone to Testosterone: suggesting an inhibitory activity in the conversion of 17-OH progesterone to Testosterone in obese men.

Lipoprotein lipase is important in the uptake of Fatty acids into cells: particularly adipose cells and muscle cells.

Testosterone inhibits lipid uptake into adipocytes.  Testosterone inhibits lipoprotein lipase.  Testosterone stimulated lipolysis.  Testosterone inhibits adipocyte differentiation of proginator cells. DHEAs effects are through different mechanisms.   Both have a preference for activity with visceral adipose tissue.

good review of the current understanding of kisspeptin and gonadotropins.

Opinion publication recommends total Testosterone as primary means of evaluating Testosterone.  This recommendation relies on the use of immunoassay techniques which can lack specificity compared to newer LC/MS and GC/MS techniques.  The authors did recommend using salivary Testosterone when borderline and SHBG variables play in, which happens to be most clients I see.  The best approach is to use both simultaneously to give a more clear physiologic picture to start.

Two percent of Testosterone is free in study of 11 normal men.  53-55% bound to albumin and 43-45% bound to SHBG.