Monitoring bone density in hypogonadal men by quantitative phalangeal ultrasound

Monitoring bone density (BMD) in hypogonadal and testosterone (T) substituted men is a major component of andrological therapy and is performed by methods that are cost-intensive and use radiation, such as quantitative computer tomography (QCT). Therefore, we assessed the feasibility of a more practical and inexpensive approach through application of phalangeal quantitative ultrasound (pQUS; IGEA DBM BP Sonic 1200, Sensweiler, Germany) in a cross-sectional study of 521 men, aged 18–91 years (224 healthy controls, 156 newly diagnosed hypogonadal, and 141 T substituted men). The method was compared with QCT of the lumbar spine in the first 80 patients. We evaluated longitudinal changes of amplitude-dependent speed-of-sound (AdSoS) in 54 hypogonadal men from the beginning of T substitution. AdSoS decreased with age (p< 0.0001) and with declining total T concentration, with a four to fivefold larger reduction in AdSoS for each nanomole-per-liter decrement in total T in the hypogonadal range (<12 nmol/L) compared with the eugonadal range (p< 0.0001). AdSoS was higher in eugonadal and substituted men than in hypogonadal patients (p< 0.0001, by analysis of covariance [ANCOVA]). Substituted men <50 years of age showed lower AdSoS than eugonadal men (p = 0.004) and untreated men with secondary hypogonadism had lower values than men with primary hypogonadism (p = 0.005). Therapeutic effects were seen regardless of age, diagnosis, or T substitution modality. In the longitudinal approach, AdSoS increased from 1986 ± 93 to 2035 ± 77 m/sec over 237 ± 57 days with the highest gain in those men with initially the lowest values (p< 0.0001, by ANCOVA for repeated measurements). In comparison to QCT, patients with a lumbar content of hydroxylapatite of <100 mg/cm3 were reliably identified by pQUS (cutoff level 1965 m/sec, T score −3.5 based on eugonadal subjects; receiver operating characteristics: area under the curve [AUC] 0.94, sensitivity 94.1, specificity 92%, p< 0.0001), but specific values of lumbar BMD could not be predicted by pQUS. pQUS represents a feasible, sensitive, and inexpensive method for assessing bone tissue in hypogonadal men over the full age range and also for monitoring the effects of T substitution.