Testosterone levels

Testosterone declines slowly as men age after peaking in early adulthood.(1) Young men have a higher nightly production (approximate minimum, 500-600 ng/dl, around 20.00 hours, maximum, 550-750, around 06.00), than older men (min, 300-500 ng/dl, around 20.00 hours, max, 350-550, around 06.00). No circadian variation at all is seen in hypogonadal men (<300).(2) At high age levels may be deficient and cause a lower quality of life.

Studies of seasonal testosterone level variations are contradictory though. A large Norwegian study indicates that levels are higher in winter and lower in summer.(3) It has been speculated if this is due to longer time spent awake or lower melatonin levels in summer, due to the longer hours of light. It would be interesting to see if men borne and living in the tropics or in temperate zones, with less cold than Norway, but still marked seasonal variation in insolation, show similar seasonal testosterone variation.

REM sleep is important in nightly production. See coming post for details.

Testosterone levels do also seem to be slightly higher in “western” men than others, but it is unclear whether this reflects nutrition, socio-economic status, disease incidence, selection bias etc. Additional information is found in “Prevalence of Symptomatic Androgen Deficiency in Men”,(4) but do also see the BACH survey.(5)

Low levels cause depression, diminished cognitve abilities, lowered aggressiveness, visceral obesity, lowere libido, osteoporosis, dry skin, anemia, loss of muscle mass, cardio-vascular disease, pain, headcahes, reumatoid arthritis etc.(6) On average libido and vigour start to noticeably wane at around <15 (total testosterone level), visceral obesity to be notable at around <12 nmol, depression, sleep disturbances, loss of concentration, diabetes type 2, waist circumference >102 cm at about <10 nmol, hot flushes, erectile dysfunction at around <8 nmol. These changes are independent of age and there are notable individual and daily differences.(7) This condition is usually called hypogonadism in developed stages. The more general term testosterone deficiency syndrome has also been suggested.

For practical reasons free testosterone should be measured as that is more indicative due to great intraindividual variation SHBG levels. (See following post.)

Andra bloggar om CPPS, kroniskt bäckenbottensmärtsyndrom, testosteron, androgener
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(1) Yeap BB. Testosterone and ill-health in aging men. Nature Clinical Practice Endocrinology & metabolism. 5(2):113-121, 2009.
(2) Gupta et al. Modeling of circadian testosterone. J Clin Pharmacol 40:731-738, 2000.
(3) Svartberg J, Jorde R, Sundsfjord J, Böna, KH, Barrett-Connor E. Seasonal variation of testosterone and waist to hip ratio in men: the Tromsö study. J Clin Endocrinol Metab 88(7):3099-3104, 2006.
(4) Araujo AB, Esche GR, Kupelian V, O'donnell AB, Travison TG, Williams RE, Clark RV, McKinlay JB. Prevalence of Symptomatic Androgen Deficiency in Men. J Clin Endocrinol Metab. Aug 14 2007. [Epub ahead of print]
(5) Araujo AB, Esche GR, Kupelian V, O’Donnell AB, Travison TG, Williams RE, Clark RV, McKinlay JB. Prevalence of symptomatic androgen deficiency in men. J Clin Endocrinol Metab 92(11):4241-4247, 2007.
(6) Bain J. The many faces of testosterone. Clinical Interventions in Aging 2(4):567-576, 2007.
(7) M Zitzmann, Testosterone deficiency and mens' health, EAU Congress 2009.