Testosterone (T) is crucial for various body functions in men, and understanding variations in T levels during the day can help health care professionals get a better understanding of a man’s health. Low testosterone, combined with symptoms like low sex drive and fatigue, is called testosterone deficiency (TD), affecting many men.

T levels tend to peak in the morning and drop in the afternoon. Therefore, a new study aimed to assess the extent of T decrease throughout the day in men with symptoms of TD and identify factors influencing it. The authors of the study sought to explore how age might affect this variation, as well as classify predictors of these fluctuations.

The researchers used their institution’s database to find men with symptoms of TD who had blood samples collected in the morning (before 10 AM) and in the afternoon (after 2 PM) within a maximum period of 3 months. Patients with a history of certain medical treatments affecting T levels such as orchiectomy, androgen deprivation therapy, and T-replacement therapy were excluded from the study. Total T was measured using a highly accurate method called liquid chromatography–tandem mass spectrometry (LCMS), which is considered by the American Urological Association to be the gold standard for measuring total T.

Statistical analyses compared T levels between morning and afternoon samples, considering changes greater than 100 ng/dL significant. They also looked at correlations between T level changes and patient age, along with other factors like diabetes and vascular conditions. Multivariable analysis aimed to identify predictors of significant T level decreases in the afternoon.

In the study, 506 men with a median age of 65 years were analyzed after exclusions. Morning T levels were similar to afternoon levels, with a median of 387 ng/dL in the morning and 373 ng/dL in the afternoon.

Most men (63%) had no significant T level difference between morning and afternoon, but 24% experienced a >100 ng/dL decrease, and 13% had a >100 ng/dL increase. Younger men showed more significant variations in T levels. Those under 30 had the most significant decrease, while older age groups had less change. Men with higher morning T levels experienced a more substantial afternoon decline. Age and baseline T levels above 400 ng/dL were predictors of a >100 ng/dL afternoon T decrease.

This data sheds light on how T levels vary throughout the day and their association with age and baseline T levels.Top of Form While some studies suggest a consistent T decline with age, others show no significant change. The present study found that T levels remained stable throughout the day in most men, with only a slight decrease in the afternoon. Furthermore, age did not appear to predict changes in T levels, but younger men had more significant variations.

Interestingly, men with higher morning T levels experienced more substantial afternoon declines, which challenges the idea of using morning T levels alone for diagnosing TD. These findings suggest that afternoon T measurements could still be relevant for excluding TD. However, the study has limitations like retrospective design and the need for same-day T measurements. Still, understanding T variations is critical for accurate TD diagnosis and management.

References:

• Novaes, L. F., Flores, J. M., Benfante, N., Schofield, E., Katz, D. J., Nelson, C. J., & Mulhall, J. P. (2024). Analysis of diurnal variation in serum testosterone levels in men with symptoms of testosterone deficiency. The Journal of Sexual Medicine, 21(5), 408–413. https://doi.org/10.1093/jsxmed/qdae026