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ASK DR.K: Thunder from Down Under

Updated: Mar 11

Dear Dr. K, “What is the relation between ED and testosterone?”


Testosterone is the chief male hormone. It controls muscle growth, fat loss, deepens the voice, causes bodily hair growth and loss of hair on the head, and other physical male traits. Testosterone is also the fuel that feeds your sexual fire (libido). Without testosterone there is no spark to get everything moving in the right direction.


What causes low T?

The primary culprit is aging. In a man’s 30’s a gradual decline in T levels begins. T levels drop about 10% with each decade. This is a gradual decline and has been accepted as a part of growing older. Men often are not aware of the change until they look back and compare how they looked and felt in the past as opposed to today. What you once enjoyed doing is now a drudge.


A second factor in low T is obesity. Located in abdominal fat cells (aka “spare tire”), there is an enzyme called aromatase which converts T to estradiol (E), a female hormone. While men need a small amount of E to help stimulate the libido, higher levels of E can suppress the erectile response. A high E level also causes more fat to be deposited in the abdomen leading to further conversion of T to E, leading to more fat being deposited, etc. (You see the pattern here?). High E levels also cause the development of enlarged breasts (gynecomastia or “man boobs”). This not just fat but actual growth of breast. (And yes, men can get breast cancer.)


Injury or illnesses that affect the testicles (i.e. mumps) can also lead to low T production.


“Okay, so how do I know if I have low T?”

The easiest way to determine if you have low T is to get a blood test to check your T levels. You should check both total T levels and free T (the active form) as well as estradiol levels. There is a caveat about blood levels-there is a wide range in what is considered normal values (200 to 1000 ng/dl). Even with clinically “normal” T levels you still may be having the subjective signs and symptoms asso