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ABSENT DIURNAL VARIATION IN SERUM TESTOSTERONE OBSERVED IN MEN WITH BASELINE LOW TESTOSTERONE
Shlykova, N. ; Bolanos, J. ; Morgentaler, A. Men’s Health Boston
Introduction: Young healthy men demonstrate a diurnal pattern of serum testosterone (T), with highest levels in the morning, then decreasing in the afternoon and evening. For this reason, clinical guidelines recommend obtaining serum specimens for T testing in the early morning, often before 10am. However, diurnal variation is blunted in men over 40y. It is unknown whether T deficiency itself may be associated with blunted diurnal variation.
Objective: The primary objective of this study was to assess diurnal variation of serum T in men with normal and abnormally low serum T.
Methods: This was a single-center case-control study in healthy men restricted to a younger age group of 46 years or less. Blood samples were obtained from subjects at 6 time points over a 24-hour period at 3h intervals, at 8am, 11am, 2pm, 5pm, 8pm, and then at 8am the following morning. Men were categorized as having normal T if 8am serum T was >300ng/dl, and low T if <300ng/dl. Statistical analysis comparing differences between groups was performed using the paired two sample t-test. Signed informed consent was obtained from all subjects. Human subject approval was obtained from New England Independent Review Board.
Results: The study population consisted of twenty one subjects with mean age of 32y±7.9, including ten men with low T and eleven men with normal T. The highest T concentration was observed at 8am, with a mean serum T of the entire study population of 325ng/dL. The lowest T concentration was observed at 2pm, with mean T of 287ng/dL. Mean T levels at 8am were 423ng/dl for the normal group and 228ng/dl for the low group (p¼0.008). At 2pm these values were 358ng/mL and 218ng/mL, respectively (p¼0.019). Serum T concentrations declined by 64ng/dl (15%) from 8am to 2pm in the normal group and by 10ng/dl (4%) for the low group. This decline was significantly greater for the normal group (p¼0.0003). The decline for the low group was not statistically significant (p¼0.54). Mean luteinizing hormone concentration at baseline was 5± 2.39 (1.8-8.5) for the entire group. Hypothesis testing led us to reject the null and conclude there is significant diurnal variation in T concentrations for men with normal levels, but not for men who are T-deficient.
Conclusion: Diurnal variation was not observed in testosterone-deficient men, suggesting an abnormality in the hypothalamic-pituitary-gonadal axis. This finding has implications for understanding the underlying pathophysiology of testosterone deficiency, and may also have clinical implications for recommendations regarding the diagnosis of testosterone deficiency (hypogonadism).
Shlykova, N. ; Bolanos, J. ; Morgentaler, A. Men’s Health Boston
Introduction: Young healthy men demonstrate a diurnal pattern of serum testosterone (T), with highest levels in the morning, then decreasing in the afternoon and evening. For this reason, clinical guidelines recommend obtaining serum specimens for T testing in the early morning, often before 10am. However, diurnal variation is blunted in men over 40y. It is unknown whether T deficiency itself may be associated with blunted diurnal variation.
Objective: The primary objective of this study was to assess diurnal variation of serum T in men with normal and abnormally low serum T.
Methods: This was a single-center case-control study in healthy men restricted to a younger age group of 46 years or less. Blood samples were obtained from subjects at 6 time points over a 24-hour period at 3h intervals, at 8am, 11am, 2pm, 5pm, 8pm, and then at 8am the following morning. Men were categorized as having normal T if 8am serum T was >300ng/dl, and low T if <300ng/dl. Statistical analysis comparing differences between groups was performed using the paired two sample t-test. Signed informed consent was obtained from all subjects. Human subject approval was obtained from New England Independent Review Board.
Results: The study population consisted of twenty one subjects with mean age of 32y±7.9, including ten men with low T and eleven men with normal T. The highest T concentration was observed at 8am, with a mean serum T of the entire study population of 325ng/dL. The lowest T concentration was observed at 2pm, with mean T of 287ng/dL. Mean T levels at 8am were 423ng/dl for the normal group and 228ng/dl for the low group (p¼0.008). At 2pm these values were 358ng/mL and 218ng/mL, respectively (p¼0.019). Serum T concentrations declined by 64ng/dl (15%) from 8am to 2pm in the normal group and by 10ng/dl (4%) for the low group. This decline was significantly greater for the normal group (p¼0.0003). The decline for the low group was not statistically significant (p¼0.54). Mean luteinizing hormone concentration at baseline was 5± 2.39 (1.8-8.5) for the entire group. Hypothesis testing led us to reject the null and conclude there is significant diurnal variation in T concentrations for men with normal levels, but not for men who are T-deficient.
Conclusion: Diurnal variation was not observed in testosterone-deficient men, suggesting an abnormality in the hypothalamic-pituitary-gonadal axis. This finding has implications for understanding the underlying pathophysiology of testosterone deficiency, and may also have clinical implications for recommendations regarding the diagnosis of testosterone deficiency (hypogonadism).
