Testosterone is a hormone made mainly in the testes and is important in the functions of many parts of the body. In men whose testes fail to produce enough testosterone the following may occur in varying degrees - loss of libido, erectile dysfunction, hot flushes, weight gain, loss of muscle mass and bone density, irritability, poor sleep, poor memory, reduction in shaving and hair loss from the legs.
Testosterone replacement therapy my restore sexual function and libido, may improve protein and fat metabolism, prevent bone loss and result in an increase in energy levels and an improved sense of well being.
The diagnosis of low testosterone is based on taking into account the symptoms a patient has and the results of testosterone blood test. There is uncertainty about the interpretation of testosterone blood levels for the following reasons.
There is a large natural variation in the levels over a 24 hour period. The blood test needs to be done between 9-10am to ensure the most accurate results. Shift work and jet lag make the interpretation harder as the body clock is disrupted.
Testosterone exists in a number of forms within the blood stream - some active and some inactive. In an ideal world we would wish to measure only the active component but to date this has not proved possible. The total level of testosterone is a guide to the active level but can be unreliable in certain circumstances.
Currently if the levels are above 12nmol/l they are thoguht to be normal, below 8 nmol/l abnormal, and uncertainty exists in patients where the level is between 8-12. In these cases if a patient has symptoms suggestive of a low testosterone level treatment with testosterone replacement can be considered and the clinical response evaluated.
Testosterone can be administered as a gel that is absorbed through the skin (tostran gel, testogel, testim gel), an intramuscular injection given every 10-14 weeks (nebido), a buccal adhesive tablet (striant), or as oral tablet (restandol). Each of these options have advantages and disadvantages.