Testosterone: when is “low” too low?
For any given person, free testosterone is a set fraction of the total testosterone. Testosterone deficiency (TD) happens in any given person when there is insufficient supply of free testosterone to bind to enough of the androgen receptors. This is termed the threshold level. What happens then, is biochemistry; see symptoms →
This threshold level can vary dramatically in different guys. It could be anywhere from 250 – 700. What’s more, is different guys reach this critical low threshold level at different ages, 25-70 years of age.
Get tested to determine your Testosterone level
What are the symptoms of
Testosterone Deficiency (TD)?
Decreased muscle mass and strength
Poor recovery after workouts
Joint pain or stiffness
Insulin resistance and diabetes
Heart disease
Anemia
Osteoporosis
Low libido
Erectile dysfunction
Rapid Aging
Fatigue or low energy
Poor stamina
Blunted motivation
Decreased athletic or work performance
Depression
Memory problems
Decreased mental clarity
Irritability
Weight gain, especially around the middle
What is Testosterone?
The testosterone molecule is a lipid (fat) soluble ligand or messenger that, in its free form, can transport into a target cell, bind with the androgen receptor, then transport to the nucleus where the testosterone-receptor complex changes the gene expression and function of that target cell.
Free or total, what's the difference?
The vast majority of testosterone that resides in blood and tissue is bound by blood proteins that are made in the liver. Blood and tissue are mostly aqueous (water), and so a lipid (oil) soluble solid molecule like testosterone can only be suspended in blood if it is carried by a water-soluble protein. Only a small fraction of that total testosterone (1-3%) is free or disassociated and able to go into the cell, bind, and do the work of testosterone.
It is most common to measure total testosterone, not free testosterone. Testosterone Cypionate is the most common pharmaceutical form of commercially supplied testosterone. The supplied or administered form of testosterone is biomimetic because it is not the same chemical composition as endogenous testosterone but there is very little difference, and most importantly, the body recognizes it as the same. When we measure total testosterone in a person the laboratory tests read the sum of the total of both endogenous and supplied testosterone.