Volume 187 - Issue 1
Revisiting the metabolic syndrome
Authors: Gerard T Chew, Seng Khee Gan and Gerald F Watts
Med J Aust 2007; 187 (1): 61. || doi: 10.5694/j.1326-5377.2007.tb01132.x
Published online: 2 July 2007
Published online: 2 July 2007
In reply: We thank Tuomainen for his interest in our review article, and for sharing with us his data showing an inverse association between fasting serum insulin levels and calculated serum free testosterone levels. We were cautious in our statement about the relationship between hyperinsulinaemia and free testosterone levels, as there are conflicting data in the literature regarding this,1,2 and few studies that directly measure free or bioavailable testosterone. Moreover, there is ongoing controversy about the calculation of free testosterone levels using total testosterone and sex hormone-binding globulin concentrations, with the validity and assumptions of some of these widely used estimation equations being called into question.3,4
We also echo the concerns of Allan et al5 about the potential pitfalls of diagnosing hypogonadism based on testosterone levels only. As the presence of low total (and even calculated free) testosterone in obese men may not necessarily reflect deficient androgen action, the diagnosis of androgen deficiency should only be made in the context of supportive clinical features. Furthermore, in abdominally obese men with the metabolic syndrome, levels of sex hormone-binding globulin and both total and calculated free testosterone can increase following weight loss,6 thereby obviating the inappropriate use of testosterone supplementation in such patients.
References
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- Simon D, Charles MA, Nahoul K, et al. Association between plasma total testosterone and cardiovascular risk factors in healthy adult men: The Telecom Study. J Clin Endocrinol Metab 1997; 82: 682-685. 0_CBBDIGFH
- Ly LP, Handelsman DJ. Empirical estimation of free testosterone from testosterone and sex hormone-binding globulin immunoassays. Eur J Endocrinol 2005; 152: 471-478. 0_CBBBCCEI
- Liu PY, Death AK, Handelsman DJ. Androgens and cardiovascular disease. Endocr Rev 2003; 24: 313-340. 0_i1091822
- Allan CA, Strauss BJ, Burger HG, et al. The association between obesity and the diagnosis of androgen deficiency in symptomatic ageing men. Med J Aust 2006; 185: 424-427. 0_CBBIBFGJ
- Niskanen L, Laaksonen DE, Punnonen K, et al. Changes in sex hormone-binding globulin and testosterone during weight loss and weight maintenance in abdominally obese men with the metabolic syndrome. Diabetes Obes Metab 2004; 6: 208-215. 0_CBBIFHDE