Tagawa et al. investigated the possible mechanism behind the weight loss effects of DHEA and found that there is a direct inhibitory effect of DHEA on glucocorticoid (re-)synthesis in adipose tissue:
Using differentiated 3T3-L1 adipocytes, we demonstrated that DHEA inhibited 11β-HSD1 activity at a concentration of 1 μM within 10 min. Inhibition was also observed in a cell-free system comprised of microsomes prepared from rat adipose tissue and NADPH, a coenzyme of 11β-HSD1. A kinetic study revealed that DHEA acted as a non-competitive inhibitor of 11β-HSD1. Further, DHEA did not inhibit 11β-HSD type 2, which inactivates cortisol or corticosterone in tissues involved in water and electrolyte metabolism, in rat kidney microsomes at a concentration <25 μM. Moreover, no conversion from DHEA to other sex steroid hormones or their precursors was observed under the present experimental conditions.These are three significant observations. Firstly, the presence of DHEA inhibits the synthesis of cortisol via 11Beta-HSD1. Secondly, it does not prevent exogenous cortisol to be converted to the "inactive" cortisone via 11Beta-HSD2 and thirdly, the dreaded conversion into estrogen, testosterone or DHT does not take place. All this would make the naturally occurring hormone DHEA a perfect selective 11β-HSD1 inhibitor, of which Stewart et al. from the University of Birmingham write (Stewart. 2011):
Selective 11β-HSD1 inhibitors lower blood glucose, improve insulin sensitivity and cause weight loss in animal models. Biomarkers have been validated to confirm target inhibition in primate and human studies. Recent clinical trials show reduction in HbA1c and blood pressure in obese patients with diabetes mellitus who have failed on metformin therapy. Potentially the therapy offers a ‘magic bullet’ for patients with Metabolic syndrome with reduced blood glucose accompanying improved insulin sensitivity, lower lipids and blood pressure and reversal of hepatic steatosis secondary to reduced autocrine generation of cortisol in liver, adipose tissue, pancreas and muscle. Liabilities include activation of the HPA axis secondary to increased cortisol clearance with hyperandrogenism, though the extent and significance of this is debated.One thing, though, before you now go about eradicating cortisol to zero. Your body needs a healthy level of cortisol to function. It goes hand in hand with thyroid hormone, helps you manage stress, perform in the gym and is even necessary to "burn" body fat. Again, moderation is key and you certainly want to know where you stand before you start tweaking your cortisol levels into the wrong direction.