Why are testosterone replacement standards and prescribing processes so frequently misguided?
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This blog post is a follow-up to the ZRT Andropause webinar.
I like to think of SHBG as a sponge that soaks up androgens and to some degree estrogens as well.
SHBG, or Sex Hormone Binding Globulin, controls testosterone effect in both men and women by modulating changes in sex steroid levels. When SHBG goes up, free testosterone goes down.
Since it binds so specifically and tightly to testosterone, it makes up part of the equation that equals androgen excess or androgen deficiency. Knowing how to manipulate SHBG can be a useful tool in a number of scenarios.
The testicles of a man in his 20s are known to contribute about 5-10mg of testosterone per 24-hour day and levels of total testosterone in the venous blood with that amount are observed to yield roughly 300-1200 ng/dL in the morning at the diurnal peak. Testosterone, whether endogenous or given exogenously, negatively feeds back on the hypothalamus, limiting GnRH and thus LH and FSH from the pituitary. A man taking supraphysiological doses of testosterone can expect to have very low or undetectable levels of LH and FSH in the serum. What happens when the prescription dose overshoots the patient's optimal dose? Certainly, we see LH and FSH practically disappear.