Why We Get the Flu in Winter, Why We Are Fat, and Other Things… The Importance of the Testosterone – DHEA Ratio


Copyright 2004, James Michael Howard, Fayetteville, Arkansas, U.S.A.  (Note:  The peak of infections because of reduced DHEA may also appear in times of strong sunlight, such as summer months.  Strong sunlight will reduce melatonin production which will decrease the “melatonin – DHEA cycle” and reduce DHEA levels resulting in increased infection rates.  March 31, 2004.)


It is my hypothesis that mammals evolved because of increases in dehydroepiandrosterone (DHEA).  The DHEA increased energy production from fat.  Hence, mammals are “warm blooded.”  Furthermore, I suggest primates arose from other mammals because of increases in testosterone.  Humans continued along this path; we produce the most testosterone.


Humans produce so much testosterone, the ratio of testosterone to DHEA may produce some benefits and some advantages.  DHEA is the active molecule, DHEAS (DHEA sulfate) is the large reservoir of DHEA in our blood.  The trouble with the ratio of testosterone and DHEA is that testosterone may interfere with the transformation of DHEAS into DHEA.  Testosterone inhibits steroid sulfatase.  Steroid sulfatase makes DHEA from DHEAS.  This may be the real reason for the evolution of humans from other primates.  Increased testosterone in women would increase their DHEAS at the expense of their DHEA.  Women would become fat and testosterone would increase the sex drive of women.  Fat is a good thing when the climate is cold.  Increased fat and sex drive in females will increase offspring when the climate is cold, and when the climate is warm.  (Human males and females produce more testosterone than chimpanzee males and females, respectively.)  Again, it is that ratio thing.


Now, it is known that testosterone decreases the effectiveness of the immune system while DHEA increases the effectiveness of the immune system.  Testosterone in people increases in the autumn and winter.  DHEA sulfate is also higher in the autumn and spring.  I suggest the reason is that increased testosterone of autumn and winter reduces production of DHEA from DHEA sulfate.  This may be the reason that infections, such as influenza increase in the winter.  It may also produce more fat in us during the autumn and winter.  It certainly is not nice to get the flu, but fat is certainly nice if we want to get pregnant in the autumn and winter and have lots of fat for our babies’ growth when it is needed.  Again, this is human evolution determined by females.


It is part of my work that many mental illnesses result from low DHEA during growth and development of the brain and these are exacerbated by low DHEA.  Therefore, I would predict that mental disorders should increase in severity and incidence in winter.  This is the case.  Now, you need to know that, according to my work, the level of DHEA determines the strength of motivation.  (This is derived from my explanation of the “fight or flight mechanism” which suggests that higher DHEA increases motivation.)  Therefore, I have to explain that the increased ratio of testosterone to DHEA in winter reduces DHEA so this should be a time when behaviors that we control are reduced.  I suggest the increased testosterone to DHEA ratio reduces our ability to control our impulses, but it may also reduce actions based on those impulses.   …unless one is provoked.


In the case of homicides, suicides, voluntary aggression, etc., a number of studies indicate that, in fact, winter is a time of reduced behaviors of this sort.  “Referrals” for disciplinary actions in schools actually decline in the winter.  In winter, we have less DHEA to act on our actions.  However, as in the case of the mental disorders and infections mentioned above, there are consequences of the increased testosterone to DHEA ratio of winter.  DHEA is very low in the elderly and the very young.  I think very low DHEA results in death.  Winter is a time of increased mortality in young children and the elderly.  Low DHEA has been linked to depression; this may be the mechanism of seasonal affective disorder or SAD.  Venous thromboemolism exhibits a higher incidence in winter.  I suggest cancer may be triggered by low DHEA.  There is a significant excess of childhood acute lymphocytic leukemia in winter.  A study in Poland found increased type 1 diabetes mellitus in autumn and winter months.  I think preeclampsia is a disorder of low DHEA and high testosterone; in one study, August had the lowest risk of preeclampsia while “the risk was highest in the winter months.”  Sudden infant death syndrome, another I attribute to low DHEA, is higher in the winter and in boys.  This list could be expanded.


Often reports of diseases and season of occurrence are conflicting, often involving infectious agents.  The testosterone – DHEA ratio should increase infections primarily in winter.  However, as pointed out above, motivation increases when DHEA begins to increase as testosterone declines with spring and summer.  Therefore, many infectious diseases will increase because of increased activities which increase infections.  This will be difficult to differentiate.  However, a pattern does emerge in many of these with increased rates cited in the literature for both autumn-winter and spring-summer, that is, two peaks.


Humans may be animals that evolved because of increased testosterone.  This produces benefits and disadvantages.  Larger brains are one result.  However, I suggest testosterone levels periodically increase and skew the effects of testosterone towards the negative aspects.  That is, I suggest people of higher testosterone reproduce faster than those of lower testosterone.  Therefore, they will increase in percentage within populations with time.  This is how “testosterone increases” and is the cause of the “secular trend,” the increase in size of children and earlier puberty that is real and robust in the United States as well as other countries.  The negative aspects of testosterone are increasing.  The examples I mentioned above are increasing as well as will others not mentioned.  We are getting fatter, sexier and infections are increasing.