November 27th, 2011 § § permalink
Bob recently asked about using hCG (human chorionic gonadotropin) rather than clomiphene to increase testosterone. As I explained in How Clomid Works in Men, clomiphene stimulates the pituitary to make luteinizing hormone (LH), which then acts on the Leydig cells in the testis to make testosterone. So why not use LH directly?
One way to take over the pituitary’s production of its reproductive hormones is to use human chorionic gonadotropin (hCG), which looks like LH to the body. It effectively stimulates the Leydig cells to make testosterone. But it’s expensive and must be injected. So if the pituitary is working, clomiphene may be a better choice to start. If the pituitary isn’t working, hCG can be tried. But if the man’s LH is already very high, neither clomiphene or LH will help all that much, as the man’s body is already trying that strategy by itself.
The pituitary also makes follicle stimulating hormone (FSH), which acts on the Sertoli cells around the developing sperm cells. To help stimulate the making of sperm in the testis, recombinant FSH (rFSH) or human menopausal gonadotropin (hMG) may be used. Like hCG, these drugs are expensive and must be injected.
Thanks for the question, Bob!
June 7th, 2011 § § permalink
May blew by, and I didn’t manage a single new post. The annual meeting of the American Urological Association and a big burst of research activity in my bioengineering lab did keep me busy, but really, there’s no good excuse, and it’s time to blog again.
One very active area of this blog is How Clomid Works in Men, with over a hundred comments to date. I’m grateful to Robert for inspiring this post. His question is, are there medications that decrease estrogen?
To review how the pituitary controls the making of testosterone in the testis, testosterone is converted to the female hormone estrogen, and rising levels of estrogen tell the pituitary to make less luteinizing hormone (“LH”). The role of LH in a man is to stimulate the testis to make testosterone, and as the pituitary sees more testosterone in the blood through the lens of estrogen, it tells the testis to make less testosterone by reducing LH. I likened this negative feedback system to a thermostat and a heater: as the room becomes hotter, the thermostat turns down the heater. Clomiphene binds tightly to the pituitary, (and hypothalamus for you biological sticklers), and tricks the pituitary into thinking less estrogen is bouncing around in the bloodstream. The pituitary labors to make more LH as a result, and the testis makes more testosterone. The drug tamoxifen works in a similar way.
But Robert’s question hinted at another way to trick the pituitary: there is a way to decrease estrogen directly so that the pituitary sees less of it and makes more LH.
The enzyme aromatase turns testosterone into estrogen. Drugs like anastrozole and testolactone block aromatase, causing estrogen to decrease in the blood. The pituitary makes more LH as a result, and the testis produces more testosterone. If a man has low testosterone and high estrogen, these drugs can simultaneously increase testosterone and decrease estrogen. In a study published in the Journal of Urology in 2002, doctors Raman and Schlegel report evidence that anastrozole seems to work a little better than testolactone, at least in terms of increasing sperm production. In that study, the doctors also suggest that these drugs are best used if the ratio of testosterone is less than ten to one.
As I wrote in my post on How Clomid Works in Men, all of these drugs are off-label for use in the male, meaning that the Food and Drug Administration didn’t approve their use in men. That doesn’t mean that they can’t be used. It means that doctors need to tell patients what we know about these drugs, allowing for an informed decision on their use. It also means that many of the questions we have about these drugs don’t have answers. A good question about aromatase inhibitors in men is whether estrogen plays an important role in some health concerns in men, and if it is decreased for a long period of time, can other health problems occur? We don’t know. My current practice for prescribing aromatase inhibitors is mostly to limit their use to male fertility, and to stop the medication as soon as possible.
So there you have the two basic ways that pills can trick the pituitary into telling the testis to make more testosterone. Thanks, Robert!
April 28th, 2010 § § permalink
With the suspension of Cincinnati Reds pitcher Edinson Volquez for performance enhancing drug use and a swirl of rumors that the agent involved was clomiphene (also known as Clomid,) I thought it timely to write about how clomiphene works and how it’s used. From what I read on the internets, there is an enormous amount of misinformation floating around out there.
To understand how clomiphene works, you need to know how the pituitary controls the making of testosterone in the testis. Testosterone is made by Leydig cells in the testis, which I explained in my last post. The pituitary releases a hormone called luteinizing hormone (“LH”) that stimulates the Leydig cells to make testosterone. Testosterone is converted to the female hormone estrogen, (which I also explained in my last post,) and estrogen tells the pituitary to stop making more LH. This kind of negative feedback system is common when it comes to how hormones work. It’s just like a thermostat and heater. As the room gets warmer, the thermostat sends less electricity to the heater. When the room gets colder, the thermostat sends more electricity to the heater.
Clomiphene works by blocking estrogen at the pituitary. The pituitary sees less estrogen, and makes more LH. More LH means that the Leydig cells in the testis make more testosterone.
As I explained in my last post, giving testosterone to a man does just the opposite. The pituitary thinks that the testis is making plenty of testosterone, and LH falls. As a result, the testis stops making testosterone, and the usually high levels of testosterone in the testis fall to the lower level in the blood.
So clomiphene is a way to increase testosterone in the blood and the testis at the same time. It preserves testis size and function while increasing blood testosterone.
Unfortunately, clomiphene is not FDA approved for use in the male. Like most of the medications that we use to treat male fertility, the pharmaceutical company that originally sought approval by the FDA did it for women. Clomiphene is now generic, and it’s unlikely that anyone will pony up the hundreds of millions of dollars necessary to get it approved for the male. That’s the bad news. The good news is that it means that this medication is fairly inexpensive, cheaper than most forms of prescription testosterone. Can a doctor prescribe clomiphene for a man? Yes. It’s “off label”, meaning that it’s not FDA approved for use in men.
As a medication, clomiphene is usually well tolerated by men. In my experience, most patients don’t feel anything as their testosterone rises. Those that do feel an increase in energy, sex drive, and muscle mass, especially if they work out. Very rarely I’ve had patients report that they feel too aggressive, or too angry. Very very rarely (twice in the last 20 years) I’ve had patients report visual changes. That’s worrisome, as the pituitary is near the optic nerve in the brain, and visual changes suggests that the pituitary may be changing in size. Because the skull is a closed space, it’s alarming if anything in the brain changes in size. In the last twenty years, I’ve also had two patients who had breast enlargement (called “gynecomastia”) while using clomiphene. Needless to say, for any of these problematic side effects, the clomiphene is discontinued.
So that’s the story with clomiphene. It can be used in the male, either for fertility or low testosterone levels. It’s an off label prescription drug. It works, and is usually well tolerated by men who take it.