I am a 41-year-old woman and some blood tests showed a raised level of thyroid stimulating hormone – TSH. I've been told my pituitary gland is having to work overtime to stimulate my thyroid to produce enough thyroxine. Eventually I will have to take thyroxine tablets. What causes a thyroid gland to stop working? And does thyroid function have any bearing on fertility? I have had three attempts at IVF, but gave up due to poor response to ovulation-stimulation drugs.

I am a 41-year-old woman and some blood tests showed a raised level of thyroid stimulating hormone – TSH. I've been told my pituitary gland is having to work overtime to stimulate my thyroid to produce enough thyroxine. Eventually I will have to take thyroxine tablets. What causes a thyroid gland to stop working? And does thyroid function have any bearing on fertility? I have had three attempts at IVF, but gave up due to poor response to ovulation-stimulation drugs.

The thyroid gland produces a hormone called thyroxine. The gland is stimulated by another hormone – TSH – produced by the pituitary gland. The body has a chemical feedback system that tells the pituitary gland to produce more TSH when the levels of thyroxine fall. A raised level of TSH usually means that the pituitary gland is doing its best, but the thyroid gland is not responding. The commonest cause is an auto-immune attack on the thyroid gland by your own body. This happens more frequently in women than in men, and it is relatively common. There is a link between thyroid gland underactivity and infertility. Ovulation depends on a large number of factors, and thyroxine is one of these. So it is possible that your poor response to ovulation was caused, at least in part, by your underactive thyroid gland.

Should I drive?

SHOULD I DRIVE?

Legally, you are standing on very thin ice. Morally, in my opinion, your position is indefensible. If you read the small print on your driving licence, you will see that you are required to tell the DVLA Drivers Medical Unit of "any physical or mental disability which affects your fitness as a driver or which might do so in the future".

Unexplained blackouts undoubtedly come into this category. The fact that only one, but not both, of your doctors has advised you not to drive, is not a sufficient reason to ignore this advice. Failure to inform the DVLA is a criminal offence punishable by a fine of up to £1,000. If, after all your investigations are complete, no cause is discovered for your blackouts, you may be allowed to start driving again after six months without blackouts. If a correctable cause can be found, you may be allowed to start driving sooner. In my experience the DVLA is very sympathetic to drivers, and only revokes licences when it is absolutely necessary. You should also inform your insurance company, or you may find that your insurance is invalid. For more detailed advice, you can phone the DVLA on 0870 600 0301.

IBS Treatment

Several years ago you mentioned a new treatment for irritable bowel syndrome (IBS) called tegaserod. You said it was not yet available, but that it might be the answer to IBS sufferers' prayers. Is it available yet? Will it be the answer to my prayers? I have had IBS for many years now, and nothing seems to help, apart from staying away from my high-stress job.

Tegaserod has been developed to act on serotonin receptors in the intestine. The new drug has recently been licensed in the US, where it is being used to treat women (but not men) who have IBS that causes constipation rather than diarrhoea. At the moment it is only licensed for short-term use. Initial reports are that it helps some women, but it is clearly not going to be the answer to everyone's prayers. It is not available in the UK, and no date has been set for its launch here.

Have your say

RP, a biochemist from Cornwall, has written in about my advice on hard facts about sex:

When you answered the question about a reader's problem with his erection, one possibility that you did not mention in your response is the decline in men's blood testosterone as they age. This decline is gradual, unlike the menopause in women, but some specialists believe this "andropause" should be treated with hormone replacement therapy. To find out further information, log on to www.andropause.org.uk, the website of the Andropause Society. Treatment with testosterone can be by skin patch, a soon-to-be-available gel or by implants. There are dramatic reports of reduced fatigue and other benefits, but Viagra may still be needed to prop up that erection.

Mrs UM from London writes:

May I suggest to your reader that he tries magnetic therapy. A magnet, worn in the lower pelvic area, about two inches above the penis, could possibly do the trick. It is important though, that the magnet has a gauss rating of 2,500 or above. Research has shown that magnets improve blood circulation, which in turn could help erectile problems. Magnetic therapy is safe and non-invasive with no known side effects.

Please send your questions and answers to A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; fax to 020-7005 2182 or e-mail to health@independent.co.uk. Dr Kavalier regrets that he is unable to respond personally to questions

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