Research Review I

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Research Review

Author’s Note: Research Review will be a summary of VERY current works in the endocrinology and metabolic world from various journals and an interpretation that does NOT simply regurgitate author’s thoughts, reveal true funding sources should it impact study results, and offer us some things to think about in the world of body composition. Feel free to comment on any of the studies – offering up your own interpretation, the nature of this is to really stir up conversation on thoughts of what’s considered hot off the press. I would like to improve upon and expand this section, offering up an inclusion of more interactive process with everyone and of course, we’ll talk free stuff down the line again.

Article #1:
Mai K, Bobbert T, Kullmann V, Andres J, Rochlitz H, Osterhoff M, Weickert MO, Bahr V, Mohlig M, Pfeiffer AFH, Diederich S, Spranger J. Free Fatty Acids Increase Androgen Precursors in Vivo. [italics]J Clin Endocrinol Metab.[/italics] April 2006, 91 (4): 1501-1507.

Summary – While this is the first study to offer what may be considered reasonable evidence that elevation of FFAs increases production of androgen precursors (DHEA, androstenedione) in vivo, a few criticisms deserve note. The power of the study (greatly influenced by the lagging sample size – 8 healthy male volunteers) is grossly inefficient. How applicable the results are to the general public remains unanswered. The study ended up a comparative analysis of saline/heparin infusion versus Abbolipid (20%)/heparin infusion and was overall very short term, so a longer-term study is definitely needed.

It has been suggested in previous models (namely those reflecting women with Polycystic Ovarian Syndrome - PCOS) that elevation of circulating levels of FFAs would induce insulin resistance and hyperinsulinemia, perhaps en route to metabolic dismay, obesity, and in worst case scenario…diabetes. An interesting finding in this study was that short-term hyperinsulinemia had no effect on any of the investigated androgens, however, a corresponding insulin elevation lead to a decrease in the level of FFAs. Therefore, any direct effect of insulin might have been counterbalanced by the reduction of FFAs. In comparison, postprandial (post-meal) suppression of FFAs might explain decreased androgens after an oral glucose load.



Article #2:
Orwoll E, Lambert LC, Marshall LM, Phipps K, Blank J, Barret-Connor E, Cauley J, Ensrud K, Cummings S. Testosterone and Estradiol among Older Men. [italics]J Clin Endocrinol Metab.[/italics] April 2006, 91 (4): 1336-1344.

Summary – One landmark may be suggested by this study. It is the largest cohort (5,995 community-dwelling, ambulatory men > 65 yrs. or better stated: non-hospitalized and still able to walk around) of older men in which sex steroid levels are available, and it suggests that testosterone AND estradiol, and their free fractions, tend to decline with age even among older men. One important notable drawback is the lack of accounting for substantial variation present in men in general.

The biggest positive of this study (presented as a large multivariate analysis) is the fact that it essentially offered confirmation of the results of smaller cross-sectional and longitudinal studies:
- older men had lower testosterone, estradiol, and free fraction levels than younger men
- reduction in free testosterone levels with age is more pronounced than total testosterone
- the rate of decline is seen to approximate 10% per decade ALMOST UNIVERSALLY
- variability of estradiol levels in older men was not as pronounced as testosterone and one of the most incredible findings was likely that which could be assumed here: estradiol (namely free and/or bioavailable) levels declined with age – which has earned a mixed review in former studies, however, more often than not it is thought that estradiol levels increase – please note that this is a new rationale hypothesized for our increased interest in potential pathogenesis of osteoporosis in males
- men with the highest levels of free testosterone had approximately twice the level of estradiol than those with lower levels – which makes sense and can likely be explained by aromatase activity

One of the more interesting findings from this study was the uncovering of supported racial discrepancies. When age and BMI were adjusted for, the total levels of serum estradiol and testosterone gave us some interesting things to think about in variability. A summary of various serum values follows:

Total Testosterone: Hispanic > African Americans > Caucasian > Asian
Free Testosterone: Hispanic = African Americans > Caucasians > Asian
Total Estradiol: Asian > African Americans > Hispanic > Caucasians
Free Estradiol: Asian > African Americans > Hispanic > Caucasians
SHBG: African Americans > Caucasians > Hispanic > Asian





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