Due to the natural diurnal variation in serum testosterone levels, the guidelines recommend collecting the sample early in the morning. 2 This recommendation is based on small observational studies that included mostly men under 45 years of age, who found a significant difference in testosterone levels between samples taken early in the morning and in the afternoon, 3-5.Testosterone secretion has a daytime secretion pattern. Maximum levels are reached in the morning between 07:00 and 10:00 a.m., a minimum is observed at night and levels begin to rise again at night.10 One study found that young men (30 to 40 years old) had an average of 88.00 testosterone levels (both free and total), which were 30 to 35% higher than levels measured in the middle of the afternoon or late afternoon. This difference decreased with age and dropped to approximately 10% by age 70.
11 This decrease in the circadian rhythm of testosterone with normal aging is well described. 12 If you have one or more of the above symptoms, we'll measure your testosterone level with a blood sample. The guidelines recommend collecting a sample first thing in the morning to compensate for the natural daytime variation in testosterone levels. Testosterone levels peak around the age of 20, and then testosterone slowly declines with age.
Reducing sleep dramatically reduces testosterone levels in a healthy young person, according to a study published in the June 1 issue of the Journal of the American Medical Association (JAMA). This study confirms previous research showing that the daytime effect on testosterone levels decreases with age, at least in this group of men with erectile dysfunction. This is a small addition to your daily routine and keeps your testosterone level very stable from day to day. There will probably be few obstacles to implementing this change, unless local laboratory policies are inflexible regarding the timing of testosterone extractions.
The pulsatile nature and rhythmic pattern of hormone secretion can have important implications for measuring circulating hormone levels. The study measured total testosterone and did not take into account possible confounding factors, such as obesity or the use of testosterone replacement therapy or androgen deprivation therapy, which could affect globulin that binds to sex hormones and therefore could alter the total level of testosterone. Newborn boys have very high levels of testosterone because they need that testosterone in the womb to develop like men. Increased public awareness of androgen deficiency has led to more men being tested for testosterone levels.
SUMMARY OF THE STUDY Differences in testosterone levels are significant only in younger men. Welliver et al1 conducted a retrospective review of the medical records of a Minneapolis Veterans Affairs hospital.
