7-keto-dehydroepiandrosterone (7-keto-DHEA), also called 7-oxo-DHEA, is a metabolite of the steroid hormone precursor DHEA.[1] DHEA, in the form of its sulfate conjugate (DHEA-S), is the most abundant steroid present in human blood and has generated interest as a potential therapeutic agent in age-related and other health conditions based on studies in preclinical models.[2][3] However, DHEA is converted to androgens and estrogens, including testosterone and estradiol, and can result in sex steroid-associated side effects, such as polycystic ovaries and signs of masculinization in females.[2][3][4] Thus, 7-keto-DHEA has arisen as a promising alternative to DHEA because metabolites of DHEA, including 7-keto-DHEA, may mediate some the biological functions and physiological and clinical benefits of DHEA.[5] Importantly, unlike DHEA, 7-keto-DHEA is not converted into testosterone or estradiol.[2][6]
Like DHEA, 7-keto-DHEA is produced endogenously in the adrenal glands, gonads, brain, liver, and skin.[5][7] Physiological (serum) levels of 7-keto-DHEA vary widely among individuals; however, they appear to be similar among men and women.[8] In a 2007 study of 215 individuals without endocrine disorders (91 males and 124 females; aged 5-71 years), no significant differences in 7-keto-DHEA levels were observed between males and females.[8] The overall mean (±SD) and median of 7-keto-DHEA levels were 0.280 (±0.39) nmol/L and 0.239 nmol/L, respectively.[8]
At puberty, the level of 7-keto-DHEA rapidly increases and plateaus until approximately 35 years of age; it then decreases with increasing age.[8][9] Because the level of 7-keto-DHEA is directly related to the level of DHEA, decreasing 7-keto-DHEA levels are likely a reflection of decreasing DHEA levels, which are also known to decrease with age.[10] Therefore, it is believed that DHEA and 7-keto-DHEA supplementation may help the body maintain a more youthful state and may be beneficial to individuals with low levels of DHEA or 7-keto-DHEA.[6]
7-keto-DHEA is typically administered orally as an acetyl ester of 7-oxo-DHEA (3β-acetyl-7-oxo-DHEA or 7-oxo-dehydroepiandrosterone-3 acetate[11] ); this form (also often referred to as 7-keto-DHEA) is less susceptible to oxidation than 7-keto-DHEA during manufacturing and storage.[3][12][13] After administration, the 7-oxo-DHEA acetyl ester is rapidly converted to 7-oxo-DHEA-sulfate (7-keto-DHEA-S) in a concentration proportional to the administered dose.[6][14]
7-keto-DHEA has been shown to promote weight loss and increase resting metabolic rate in people who are overweight.[15][16][17] In two placebo-controlled double-blind trials, participants who received 7-keto-DHEA acetyl ester lost significantly more weight than those who received placebo (2000 study: mean, -2.88 kg vs -0.97 kg, respectively; P=.01[15] and 2002 study: mean, -2.15 kg vs -0.72 kg, respectively; P=.038[16]).
Another placebo-controlled double-blind study with a 3-way cross-over design evaluated the effect of 7-keto-DHEA on resting metabolic rate in adults who were overweight.[17] Participants received the 7-keto-DHEA acetyl ester (50 mg twice daily), HUM5007 (another 7-keto-DHEA acetyl ester containing supplement; 50 mg twice daily), or placebo in conjunction with a calorie-restricted diet for 7 days (each study period was followed by a 7-day washout period).[17]
7-keto-DHEA treatment increased resting metabolic rate compared with baseline levels (3.4% increase with HUM5007 and 1.4% increase with 7-keto-DHEA).[17] Treatment with either 7-keto-DHEA product significantly increased the resting metabolic rate (+134 kcal/day [7.3% increase] with HUM5007 and +96 kcal/day [5.4% increase] with 7-keto-DHEA) compared with placebo (-75 kcal/day [3.9% decrease]; P=.001 for both).[17] Therefore, in combination with a calorie-restricted diet, 7-keto-DHEA appears to not only reverse the decline in resting metabolic rate associated with dieting but to enhance it and may benefit individuals who are overweight or with impaired energy expenditure.[17]