Distinguished Professor of Urology at UCSF Discusses PFS in New Book on the 'Vast Influence of Testosterone'
Now, thanks to a Distinguished Professor of Clinical Medicine and Urology at the University of California, San Francisco, PFS is spilling ink not only on newsstands, but in bookstores, too.
In this new, 203-page work—which Nobel Prize winner Stanley Prusiner, MD, calls “fascinating”—Dr. Ryan “explores the complex chemical system responsible for a diverse spectrum of human behaviors and health in both men and women. [He] taps his vast experience treating prostate cancer with testosterone-lowering therapy, observing that this often leads to profound changes in the patients’ perspectives on their lives and relationships.”
And in a section titled “The Business of Baldness and the Dangers of Baldness Correction,” he discusses PFS at length.
“Propecia is a low-dose drug, and it was supposed to manipulate testosterone only in the scalp. Instead, it had done a number on Lars’s brain, bringing on episodes of depression, irritability, and aggression that changed his life,” writes Dr. Ryan of one of two PFS patients he interviewed. 
“I’m inclined to believe the medication had something to do with it,” he continues. “First, we’re not talking about just a handful of men who experienced similar symptoms in response to taking finasteride products… Second, it’s biologically plausible that finasteride was causing these problems because we know that 5AR, the enzyme that converts testosterone into DHT—the enzyme blocked by finasteride—is heavily active in the parts of the brain known as the ‘reward pathways’… impairment of these circuits can lead to a lack of enthusiasm for things like sex and work. Third, DHT and testosterone aren’t the only hormones that interact with 5AR, and in fact research into the dynamics of various hormone levels in cerebrospinal fluid had revealed that they decrease in response to finasteride or other drugs that impair 5AR.”
Then Dr. Ryan speculates on a root cause of the condition.
“A group of Italian researchers gave finasteride to rats and noticed that the number of androgen receptors in their brains went up . Moreover, the effects persisted long after the drug had been discontinued… they then called in men with PFS, took skin from the penis and found that the density of androgen receptors in men with PFS was about twice that of those without.
“Now, remember the idea of the testosterone bell curve and damping effects (little testosterone, little growth, more testosterone, more growth, even more testosterone, reduced growth)? I think this is what we are seeing here. With a greater concentration of receptors, the organ becomes more sensitive to testosterone and at a certain point, paradoxically, that sensitivity may shut down.”
Dr. Ryan earned his MD from the University of Wisconsin, and completed his residency in internal medicine at the University of Wisconsin Hospital and Clinics, where he also served as Chief Resident. He completed a fellowship in medical oncology in the Department of Medicine at Memorial Sloan-Kettering Cancer Center and the Joan and Sanford I. Weill Medical College of Cornell University in New York. To date, he has published more than 150 scholarly works on hormonal and other treatments for prostate cancer.
To learn more about Dr. Ryan’s book, visit (where, at press time, it ranked No. 42 in the Science & Math category).
As always, we remind all PFS patients who have not yet done so to report their symptoms to the FDA’s MedWatch program as directed here . Those living outside the US should also access the WHO’s Collaborating Centre for International Drug Monitoring list of pharmacovigilance agencies and report to their respective health agency.
And of course, if you or a loved one are suffering from PFS, and feeling depressed or unstable, please don’t hesitate to contact us as soon as possible via our Patient Support hotline:
Thank you.

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