Purpose: The thresholds for testost erone (T) and the symptoms required for defining late onset hypogonadism (LOH) are under debate. The aims of the study are: (1) to verify the association between total and calculated free T (cfT) and sexual symptoms and (2) to identify thresholds for total and calculated free T to discriminate symptomatic from asymptomatic men.
Methods: A consecutive series of 4890 men attending the outpatient clinic for sexual dysfunction was retrospectively studied. Biochemical parameters were collected. The relationships between symptoms and total or calculated free T were evaluated as LOESS curves.
Results: Severe impairment in morning erections, low libido and ED were reported by 14.6, 2.7 and 60.2 %, respectively. Simultaneous presence of severe ED and impaired morning erections or low desire was reported by 12.7 and 1.9 %, respectively. Severely reduced desire and morning erections were complained of by 1.0 %. The simultaneous presence of the three severe sexual symptoms was reported by 0.8 %. Receiver operating characteristic (ROC) curve analysis showed that the highest accuracy for total T and cfT in detecting subjects with two symptoms was observed for reduced morning erections and desire (area under the ROC curve [AUC] = 0.670 ± 0.04 and 0.747 ± 0.04, for total T and cfT, respectively, both p < 0.0001). The addition of the third symptom, ED, further improved the accuracy (AUC = 0.681 ± 0.05 and 0.784 ± 0.04, for total T and cfT, respectively, both p < 0.0001). The assessment of the Youden index showed that the best thresholds for detecting men with androgen deficiency-related symptoms are 10.4 nmol/L for total T and ranges 225-260 pmol/L for cfT.
Conclusions: The simultaneous presence of reduced morning erections and desire is the cluster of symptoms that, along with total T < 10.4 nmol/L or cfT <225 pmol/L, defines LOH in a specific, evidence-based manner.
Keywords: Definition; Erectile dysfunction; Hypogonadism; Impaired morning erections; Low libido; Sexual symptoms.