The ZRT Laboratory Blog

The ZRT Blog is an extensive resource for patients and health care providers searching for health and hormone testing information. Here, you can read about ZRT’s cutting edge research, advances in testing, wellness advice, and health industry highlights.

Topical Testosterone & the U-Shaped Curve

Posted by Dr. Allison Smith on Thursday, 11 June

Drawing of testosterone's molecular structureThe 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.

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Men's Heart Health & Testosterone

Posted by Dr. Alison McAllister on Thursday, 20 February

testosterone man

Men and testosterone therapy have been a hot topic in the news recently.

Stories are filled with cautions about the use of testosterone therapy in men causing heart attacks and leading many doctors to question testosterone supplementation.

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Testosterone: Elixir or Dangerous Drug?

Posted by Dr. David Zava on Wednesday, 19 September

Mature men playing football on the beachAn FDA-approved testosterone gel was shown to significantly increase risk for adverse cardiovascular, respiratory, and dermatological events in men 65 or older who had impaired mobility and increased health risks.

This is according to a recent study published in the prestigious New England Journal of Medicine (NEJM) (1) that casts a shadow on the common use of testosterone therapy in older men for boosting their energy and vitality. 

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