There has been a major change in thinking with regard to late-onset hypogonadism, also known as andropause, a disorder that has served as the rationale for much testosterone prescribing. Fifteen years, ago based on data from the Baltimore Longitudinal Study on Aging, it was thought that up to 30% of older men have andropause; however, that conclusion was based solely on testosterone levels, with no consideration of signs and symptoms.
More recently, European investigators used an appropriately more rigorous definition of andropause: that is, a serum total testosterone level below 320 ng/mL plus at least three sexual symptoms, such as low sexual desire, poor morning erection, and erectile dysfunction. By this definition, the prevalence of andropause is much lower, a maximum of 3%-5%. And it’s influenced by advancing age, body mass index, and comorbid conditions (N Engl J Med. 2010 Jul 8;363[2]:123-35).
“The 30% prevalence figure that’s out there is just wrong,” Dr. Wierman stressed. “There may be a diagnosis of late-onset hypogonadism – it’s a diagnosis of exclusion – but it’s much lower.”
In a follow-up study, the same European researchers showed that weight loss in middle-aged and older men was associated with a proportional increase in serum testosterone and sex-hormone binding globulin, while weight gain brought a proportional drop in testosterone and SHBG (Eur J Endocrinol. 2013 Feb 20;168[3]:445-55).
Dr. Wierman said this study contains an important lesson for everyday clinical practice: In overweight older men with low-normal testosterone levels in the 200-250 ng/mL range, the primary recommendation should be diet and lifestyle modification aimed at achieving weight loss, not testosterone therapy. Successful weight loss will boost their testosterone level, improve comorbid obstructive sleep apnea, enhance their cardiovascular and metabolic fitness, and in some cases improve erectile dysfunction, although she was quick to add that low testosterone is “actually a pretty modest cause” of erectile dysfunction.
The number-one cause of erectile dysfunction is poor vascular plumbing as predicted by hypertension and hyperlipidemia. Neurogenic causes are number two and are predicted by chronic back injury, diabetes, and vitamin B12 deficiency. Hormonal causes are next, followed by performance anxiety and other psychogenic issues, and lastly iatrogenic causes involving medication side effects.
Dr. Wierman reported that she is coprincipal investigator for a clinical trial on neuroendocrine dysfunction during rehabilitation after traumatic brain injury funded by the Colorado Brain Trust. Abbvie donates the testosterone gel and placebo utilized in the study.