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Testosterone and Libido
There is much written in lay literature about the benefits of testosterone for enhancing libido. There is some truth and a lot of exaggeration. In the GYN community, I think the manufacturer of Estratest spreads some of the misinformation. Estratest (see my comments below) is the only commercial product containing “testosterone” that is FDA approved for use in menopause. I will share my experience.
Normal testosterone levels: Most labs assign a normal serum testosterone range of 30-75 ng/dl. In a healthy young woman, the ovary makes about half of the testosterone and half comes from the adrenal. The commercial laboratory normal range is two standard deviations on each side of the mean. That is 90% of the population. Only the 5% above 75 and the 5% below 30 are considered abnormal. I asked the PhDs that oversee Quest Diagnostics if they have the actual curve of distribution. Their response was no, their figures did not work that way. I suspect it is not an even distribution. PCOS is a fairly common disorder; more than 5% of the population. That means that PCOS women would pull at the top of the normal range, with testosterone levels between 60 and 90. Libido within the normal range: I see many young women with various menstrual and hormonal disorders. It is extremely rare for a patient in her teens or twenties to list low libido among her complaints (nor do young women worry about having an excessive libido). Young women with PCOS complain about acne, abnormal hair growth and irregular periods. They are not noted for excessive sexual behavior. Most commonly, I see serum testosterone in PCOS women between 60 and 90. The levels of DHEA-S and androstenedione are also elevated. They are entirely made from the adrenal origin. On the low end, it is not unusual for me to see testosterone levels below 30 in young, sexually active women, with no apparent sexual problems. Placing a woman on oral contraception suppresses ovarian testosterone production and the levels will fall. Although some individuals have reported reduction of libido on oral contraception, it is not universally or even frequently a problem. In short, for patients in their teens and twenties, I see little relationship between testosterone and libido for values within or even near the normal range. Sexual response to testosterone therapy: Occasionally I see women who have been treated by other physicians for low libido problems. One popular therapy is receiving injections of testosterone oil. These injections are usually given on a monthly basis. It is not unusual to find levels of 250-500 ng/dl in these women. Many times these are the levels of patients I have tested with naturally occurring testosterone elevation. Some women do report a significant increase in libido. I do not feel that it is ever appropriate to send a patient into extreme super-physiologic levels of any hormone. In the long run, this will probably cause hirsutism, a deepened voice and male pattern baldness. Even if no immediate problems are seen, my goal is to normalize conditions, not to turn a normal situation into an abnormal one. What determines libido? A woman’s sex drive at any point in time is multifactorial. Her general health is of great importance. Is she getting adequate exercise and rest? How does she feel about her current sexual relationship? Does she have the time and motivation to devote to her sexuality? Although libido can be improved by using extreme levels of testosterone supplementation, I have not found that raising a woman's level from low to the middle or high end of the normal range has much of an effect on libido. Does Georgia Hormones recommmend supplemental testosterone? Yes. Testosterone has a small effect on mood. It also improves decision-making. I have pointed out to patients that many men tend to make decisions more rapidly (and with more certainty) than most women. They may be wrong, but they are less frequently in doubt. In addition, testosterone stimulates osteoblasts to repair and build bone, thus protecting against osteoporosis. What is in Estratest? Estratest and Estratest HS is a brand name of two synthetic hormone sets contained in a single tablet. The estrogen part is esterified estrogens. These are various estrogens with added molecules to increase water solubility and power. The testosterone is actually methyltestosterone. This is also a synthetic molecule that stays in the body for prolonged periods because it is difficult to metabolize and excrete. Neither of these medications show up on hormone blood work. It is difficult to compare either of these medications to natural hormones because they cannot be easily measured and their exact actions are unknown. In addition, the ratio of estrogen to androgen is fixed. They cannot be custom mixed for the individual patient’s needs. Some observations about testosterone lab work: In medical literature it is frequently reported that total testosterone levels are not reliable, that they vary randomly. I don’t believe this. Laboratory testing is very precise now; it is automated and consistent. If nothing has changed for an individual patient, the values are fairly consistent and repeatable. It is common in science and in medicine that data not understood is considered to be in error. Anything that affects either ovarian or adrenal output will affect testosterone levels.
Total versus free testosterone: There is much discussion in literature of measurement and importance of total testosterone versus the free component. This involves levels of Sex Hormone Binding Globulin (SHBG). At one time I was measuring all of these levels. I generally found that total and free testosterone rise or fall together. Much of the testosterone in the blood is loosely bound to albumin. Since there is much more albumin than SHBG in the blood, this amounts to a significant portion of the total testosterone. Many things including estrogen, thyroxin, testosterone, BMI, insulin and insulin resistance affect SHBG levels. Free testosterone is not directly measured, but is mathematically calculated using SHBG levels. I am not sure if the lab numbers for free testosterone precisely reflects testosterone activity within a specific individual. Additionally, for most target tissues, testosterone must be converted to dihydrotestosterone to be active. The individual’s level of 5-alpha reductase activity governs testosterone activity at most target tissues. I have found it easier and less expensive to just measure total testosterone. All of the hormones affect the activity of each other. There is little to be gained by getting too hung up on any one blood level. My goal is to holistically balance the patient’s health and lifestyle as well as individual hormone levels. Testosterone supplementation: Bioidentical testosterone can be given in a capsule, a sublingual troche, as a topical cream, vaginal cream or topical gel. My experience is that many women have little or no rise in testosterone when given in a capsule. The topical gel can be very effective. I start with a concentration of one-half mg/ml gel and have the patient use one ml/day. Since topical testosterone can induce hair growth if put on the same patch of skin every day, I tell patients to move the site around. They have two upper arms, two lower arms, thighs front and back, a rear end and belly. There are lots of places. Most of the hormone is actually absorbed through the palm of the hand, so the site rubbed on doesn’t matter much. The alcohol-based gels are fairly rapidly absorbed and are not very messy. Some physicians have suggested putting a little testosterone directly on the clitoris. If this is done, the compounding pharmacist must be instructed to make a vaginal cream. The alcohol based gel will burn if placed anywhere on the vulva. After six weeks, serum testosterone can be tested again to check the levels. If insufficient levels have been achieved, either the concentration or quantity of hormone can be increased. There is a great deal of individual variation. Some women will have a big rise in levels with the starter concentration of ½ mg/ml. Other patients can use up to 2-3mg/ml concentration without receiving too high a level. My goal is to return testosterone (and all hormone levels) back to normal levels, as tolerated. I am never comfortable putting a patient into a superphysiologic state. If testosterone results indicate over 80mg/dl, too much is being used. Either reduce the concentration, the quantity or both. Conclusion: Testosterone is a normal component of a woman’s hormonal milieu. It is important for mood, muscle development, bone health and brain function. Supplementation can be used to bring low levels into the normal range. When supplementing testosterone, follow up blood levels are important to ensure sufficient (but not excessive) serum levels. A woman’s libido is affected by many factors in her health and life. Testosterone is only one of those factors. Raising testosterone levels from below normal into the normal range, or even to the top of the normal range, has only a small effect on libido. I do not feel it is appropriate, safe, or good medical care, to raise any hormone to super-physiologic levels. Of note: A study was recently reported in the N.A.M.S. First to Know series. A pharmaceutical company wanted to market a testosterone patch for women. There were three groups of women and each group was given a different dose level of the patch. Before treatment, each woman wrote a survey of libido and sexual frequency and activity. Repeat surveys were filled out during and after treatment. There was no statistically significant change in libido between the various levels of testosterone supplementation. No serum testosterone levels were obtained on any of the women, either before or during the trial. In my opinion, there seems to be very little reason to expect improvement in the libido if a woman already has normal testosterone levels and a physician raises the levels a bit more. Pharmaceutical companies want to treat everyone, regardless of hormonal need. We need to change this approach! Hormone balance should be the goal, not blind treatment of symptoms regardless of the cause. The FDA did not approve the patches — they may be very effective for enhancing testosterone levels. It is possible that a new approach with a goal of restoring normal hormone levels will eventually meet FDA approval. |