Diagnosing Testosterone Deficiency in Men
The diagnosis of testosterone deficiency is a combination of both clinical features and serum testosterone measures - neither in isolation is consistently reliable.
The measurement of testosterone levels in the blood provides a snapshot of what the testosterone status of the person is at the time of taking blood.
Testosterone secretion follows a diurnal rhythm in males. That is it rises and falls over a 24 hour period. Testosterone production occurs during the night and early morning with levels highest on waking. Serum testosterone levels slowly decrease during the day and are lowest in the late afternoon and early evening.
Therefore blood samples should preferably be taken in the morning, when hormones levels are at their highest. Individual variations in serum testosterone levels can occur due to time of day, medication usage, stress, illness or recent surgery.
The testes do not store testosterone. Once produced testosterone is secreted into the blood stream where it is rapidly adhered to by the protein sex-hormone binding globulin (SHBG).
SHBG is a transporter protein found in the blood. It acts as a carrier to move hormones around the body. Up to 99% of testosterone produced is bound to SHBG. Testosterone to which SHBG does not attach is the biologically available testosterone that is free to act on and enter into cells throughout the body. This "bio-available" testosterone is crucial in determining how well testosterone can work in the body.
Some doctors will measure only testosterone levels (called total testosterone) and not take into account the SHBG levels. While not technically wrong total testosterone measurement alone is not the most accurate representation of how much testosterone is free to act in the body. As a consequence the total testosterone reference ranges commonly adopted by pathology laboratories for determination of "normal" and "low" testosterone are potentially misleading, especially in the determination of late-onset hypogonadism because the results do not take into account the effects of SHBG. SHBG is elevated with ageing, smoking, high alcohol intake, insulin, oral estrogens and some medications.
In order to establish an accurate diagnosis for a patient it is essential to measure the "free androgen index" or FAI. This is calculated by the total testosterone level in the blood divided by the SHBG level multiplied by 100.
Pathology labs will automatically do this calculation and the result will be the FAI reading. Generally a FAI reading of 70 or less is a cause for concern and a reading below 50 may be a strong indication that testosterone supplementation is warranted. Other factors such as pre-existing illnesses, physical, hormonal, psychological and mental health must be taken into account by the doctor before routine prescribing of testosterone.
Whether due to testicular or brain or ageing the signs and symptoms as a result of the androgen deficiency are consistent.
Individuals may exhibit some or all of the following:
- Changes in mood (fatigue, depression, anger)
- Decreased body hair (feminization)
- Decreased bone mineral density and possible resulting osteoporosis
- Decreased lean body mass and muscle strength
- Decreased libido and erectile quality
- Increased abdominal fat
- Rudimentary breast development (man boobs)
- Low or zero sperm in the semen.
The diagnosis of hypogonadism can be facilitated through the use of the AMS (Aging Males' Symptoms) rating scale.
The Ageing Males Symptoms (AMS) questionnaire is a 17 question self-rating symptoms based questionnaire with three key domains of assessment - mind (5 questions), body (7 questions) and sexual (5 questions). Responses to each question are assigned a rating 1-5 (none to extremely severe) and the total sum of all subscales provides a total score. Scores can range from a total low of 17 to a maximum of 85, with a complaint score measuring greater than 50 considered severe.
The AMS is well suited to assist in both the diagnosis of testosterone deficiency and for the monitoring of treatment in patients using testosterone replacement therapy.
Once it has been determined that an individual is testosterone deficient through biochemical and clinical assessment testosterone replacement therapy (TRT) can be considered.
It is imperative that prostate or breast cancer be excluded prior to initiating TRT.
To exclude prostate cancer a doctor will conduct an examination of the prostate gland. This is done via insertion of the doctor's finger into the rectum of the patient and feeling the size and hardness of the prostate gland. This technique is called a digital rectal examination (DRE) and doctors are well trained in this technique. Also a blood test to measure a component in the blood called serum prostate-specific antigen (PSA) is conducted. Both these tests should be conducted prior to commencing testosterone therapy and are mandatory in men over the age of 40 years.