Reporting and ideal testosterone levels in men undergoing androgen deprivation for prostate cancer-time for a rethink?

A population K-PD model analysis of long-term testosterone inhibition in prostate cancer patients undergoing intermittent androgen deprivation therapy

Intermittent androgen deprivation therapy with gonadotropin-releasing-hormone (GnRH) agonists can prevent or delay disease progression and development of castration resistant prostate cancer for subpopulations of prostate cancer patients. It may also reduce risk and severity of side effects associated with chemical castration in prostate cancer (PCa) patients. One of the earliest comprehensively documented clinical trials on this was reported in a Canadian patient population treated with leuprorelin preceded by a lead-in with cyproterone acetate. A systems-based mixed effect analysis of testosterone response in active and recovery phases allows inference of new information from this patient population. Efficacy of androgen deprivation therapy is presumed to depend on a treshold value for testosterone at the nadir, below which no additional beneficial effects on PSA reponse can be expected, and occurance of testosterone breakthroughs during active therapy. The present analysis results in a mixed effect model, incorporating GnRH receptor activation, testosterone turnover and feedback mechanisms, describing and predicting testosterone inhibition under intermittent androgen deprivation therapy on the individual and population level, during multiple years of therapy. Testosterone levels in these patients decline over time with an estimated first order rate constant of 0.083 year^-1(T_1/2 = 8.4 y), with a substantial distribution among this patient population, compared to the general population. PCa patients leaving the trial due to unmanageble PSA relapse appear to have slightly higher testosterone levels at the nadir than sustained responders. These findings are expected to contribute to an increased understanding of the role of testosterone in long term disease progression of prostate cancer.

Measurement of Serum Testosterone in Nondiabetic Young Obese Men: Comparison of Direct Immunoassay to Liquid Chromatography-Tandem Mass Spectrometry

Hypoandrogenemia, a frequent finding in men with obesity, is defined by low concentrations of serum testosterone. Although immunoassay (IA) is the most used method for the determination of this steroid in clinical practice, liquid chromatography-mass spectrometry (LC-MS/MS) is considered a more reliable method. In this study, we aimed to compare IA versus LC-MS/MS measurement for the diagnosis of hypoandrogenemia in a cohort of 273 nondiabetic young obese men. Mean total testosterone (TT) levels were 3.20 ± 1.24 ng/mL for IA and 3.78 ± 1.4 ng/mL for LC-MS/MS. 53.7% and 26.3% of patients were classified as presenting hypoandrogenemia with IA and LC-MS/MS, respectively. Considering LC-MS/MS as the reference method, sensitivity and specificity of IA were 91.4% (95% CI 82.3-96.8) and 61.1% (95% CI 54.0-67.8), respectively. IA presented an AUC of 0.879 (95% CI 0.83-0.928). Multivariate regression analysis indicated that sex hormone-binding globulin (SHBG) concentrations (p = 0.002) and insulin resistance (p = 0.008) were factors associated with discrepant IA values. In conclusion, the determination of TT by IA in nondiabetic young men with obesity yields lower concentrations of TT than LC-MS/MS, resulting in an equivocal increased diagnosis of hypoandrogenemia, which could lead to inaccurate diagnosis and unnecessary treatment.