Howard S Jacobs
Emeritus Professor of Reproductive Endocrinology

We all know something about sex, many know something about hormones but I'm afraid there are some weird ideas floating about where the two of them are concerned. I'll try to give some factual information here. As always, if I've left you with ambiguities and uncertainties, I want to apologise and suggest you take the problem to your family doctor or Endocrinologist for a full, and I hope, frank discussion and, hopefully, some effective treatment too.

Let's start with essential terminology: when we talk about sexual desire, our sense of excitement when we feel sexually aroused, we use the term libido. It's a neutral term, in the sense that it tells you nothing about the person's sexual orientation, that is, whether they're attracted to someone of the opposite (heterosexual) or of the same (homosexual) sex. So far as we know, sexual orientation has nothing to do with hormones. It's important to distinguish problems with libido from problems with sexual function, such as erectile dysfunction (previously referred to as impotence) or difficulties with having orgasms. The reason is that many people with, say erectile dysfunction, retain their libido (for example people with diabetes) but if the point isn't made clear and they get treatment for impaired libido, the misery caused by impotence is simply compounded.

What are the conditions that cause problems with our libido? Here we are focusing on hormones but I hope no one needs reminding there's more to this than just hormones. And in the following discussion I shall be assuming the person is physically and psychologically in reasonably good health - for example, people who have clinical depression usually lose interest in sex as part of the illness.

Providing a woman has gone through puberty and has previously been functioning normally, I think the first hormonal disturbance to think about in a person complaining they've lost interest in sex is excessive secretion of Prolactin. That's the hormone which, in the normal situation (ie during breast feeding after a baby's been born), helps to produce the milk. It also stops ovulation occuring so a new mother doesn't get pregnant while she is still nursing her baby. You can see that as well as prolactin impairing ovulation, its effect on reducing libido also helps to avoid another pregnancy occuring at this metabolically demanding time. As the baby is weaned, prolactin levels fall and everything returns to normal. If one should happen to have increased prolactin secretion at an inappropriate time (Hyperprolactinaemia), that's to say, not after recent childbirth, the periods usually stop, milk may be formed (usually in small amounts) and people lose interest in sex. A return of libido is a welcome part of the response to successful treatment, whether it be with medication or by surgical removal of a Prolactinoma. Prolactin is, however, rarely the cause of the problem in a woman whose menstrual cycle is normal.

Two other points about prolactin are worth noting. The first is that the effect of excessive prolactin on stopping ovulation may be so powerful that Oestrogen secretion falls too low for the vagina to function normally. If that happens, women may find that when they do have sex they are dry inside and, because they don't make normal amounts of lubrication, intercourse is uncomfortable or even painful. The low oestrogen levels can also cause Osteoporosis (brittle bones), even in young women. I think the effects of subnormal oestrogen levels are so unpleasant and medically so important that anyone with Amenorrhoea (no periods) caused by a high prolactin level should have effective treatment to lower the levels to normal, so that these problems are put right. It's also important to check that the bones have gone back to normal with a test of bone density.

The other point about prolactin is that excessive secretion in men impairs their libido too. It can cause Testosterone levels to fall so low that they have trouble with intercourse (erectile dysfunction). They can also get osteoporosis. Needless to say these problems can usually be remedied by effective treatment of the prolactin problem.

So far as libido is concerned, the next hormone to think about is testosterone. We've mentioned one cause of subnormal testosterone secretion already but there are numerous other causes, which have to be diagnosed accurately before treatment starts. Testosterone deficiency has different effects according to when it comes on - before puberty, impairing the boy's development into a man - or after puberty, when the man will have experienced puberty and normal libido and potency, but then it all becomes lost as a result of the hormonal condition. Testosterone is important in the prenatal development of men's genitals and a deficiency that arises before birth may show up at birth as incomplete development. Severe testosterone deficiency in adult men causes erectile dysfunction, by which I mean the inability to obtain an erection sufficient to accomplish sexual intercourse.

Testosterone treatment at present is usually given in the form of intramuscular injections every three to four weeks. The amount has to be adjusted according to the man's age and it should always be started in a low dose. There are testosterone skin patches available but they can cause skin irritation; there is a less irritant patch with can be applied to the skin of the scrotum. There is also a tablet form which can be used but it has to be taken two to three per day. With this oral medication serum testosterone levels remain below normal because the hormone is converted to an active form which unfortunately does not get measured when you get the usual blood test done. This means judging the correct dose is not as simple as say, judging the dose of Thyroxine, where the correct dose is the one that produces thyroid function tests in the normal range.

Effective treatment with testosterone increases strength and stamina and causes growth of body and facial hair. It usually increases libido. Its effect on potency is variable and if erectile dysfunction continues one should consider cotreatment with Viagra. This compound works by increasing blood flow to the penis and so enhances erection. The effect of Viagra is only realised in response to sexual excitement, illustrating why it is important for pituitary patients to be sure their hormone levels are normal when they are considering treatment with Viagra.

Then there is the question of whether testosterone treatment can help women as well as man. In the normal woman more testosterone is made by the Adrenal glands than by the ovaries. Women with a pituitary disorder that has caused ACTH deficiency (ie who need to take Hydrocortisone replacement therapy) may therefore suffer from testosterone deficiency. This is not a very well documented area because the role of testosterone in women has not really been fully worked out but I think testosterone deficiency in hypopituitary women on hydrocortisone therapy lways needs to be considered, particularly if the woman has lost interest in sex. The treatment is with very low dose testosterone - the dose needs to be kept low because too much can cause problems like greasiness of the skin and spots and unwanted hair. I'm sure it should also be combined with oestrogen replacement (see below).I have to say however that while such treatment makes sense to me, so far as I am aware, there are no supporting clinical trials that evaluate its benefits and risks on a scientific basis.

To summarise thus far:

• Our libido is mainly affected by personal circumstances but hormones are important too.
• In women with amenorrhoea the endocrine condition to consider first if impaired libido is a feature is hyperprolactinaemia.
• Treatment that lowers prolactin is usually successful in restoring libido.
• The coexisting problems of oestrogen deficiency get better too but it is important to monitor the response and that includes measuring bone density.
• Testosterone deficiency in hypopituitary women should be excluded, particularly in patients needing adrenal hormone replacement therapy. I don't think testosterone deficiency is ever a problem for women with normal pituitary function, except for those with primary adrenal failure (for example Addison's disease).
• Testosterone deficiency in men can be corrected relatively easily but additional treatment with Viagra is needed if erectile dysfunction persists after testosterone is replaced. This is important because in the past men were often given progressively larger doses of testosterone if impotence persisted. On the whole testosterone is better for improving libido than potency. I hope the advent of Viagra will prevent testosterone over-dosage.

Finally, I want to talk about oestrogen replacement treatment in women. Everyone knows that after the menopause the fall in oestrogen levels can cause hot flushes and sweating attacks, vaginal dryness and discomfort during intercourse. The fall in oestrogen may also cause the development of osteoporosis (brittle bones that fracture easily) and perhaps the development of premature heart disease. Women with hypothalamic - pituitary disorders which have caused amenorrhoea are also likely to develop the problems of oestrogen deficiency, although curiously flushing and sweating attacks are not often seen. But this does mean that they should be considered for oestrogen replacement therapy - at any age - to ensure these problems don't occur. Opinion varies over which is the optimal preparation to use, some doctors recommending the birth control pill as the easiest formulation to take, others recommending preparations specifically designed for post menopausal hormone replacement. I don't know of any head-to-head comparisons of the two forms of treatment in hypopituitary women but the key points to be sure of, whichever is chosen, is that the person feels well on the treatment, understands it and has checks to ensure the dose given is adequate. The important things to note are that vaginal symptoms should disappear if the dose is adequate and that the bone density should be normal or returning to normal. Blood tests of the fats (fasting triglycerides and cholesterol) should be in the normal range. Unfortunately blood oestrogen levels are rarely of much help. It goes without saying that the usual checks on blood pressure, examination of the breasts and pelvis (and cervical smear) should be performed.

Lastly, what about sex hormone treatment of children with hypothalamic pituitary disease? The important things to remember here are the age at which puberty usually occurs, and the fact that normal puberty unfolds over about five years. There should be no rush to raise doses of hormones but equally no delay in starting treatment, albeit with very small amounts of the appropriate hormones. I think this is a subject for a separate article by a paediatric endocrinologist. Suffice it to say here that discussions should start with the endocrinologist around the age of ten, the exact timing of therapy being a matter for very careful consideration.