June 3, 2004

Q: Please comment on the reliability of blood tests for thyroid disease. I have all the symptoms of too little thyroid — fatigue, constipation and weight gain on a limited diet. According to all my blood tests (more than a dozen in my lifetime) my thyroid gland functions ok. I look forward to your explanation.

A: A poorly functioning thyroid gland, one that produces too little thyroid hormone, presents a fairly distinctive picture. Hair becomes brittle and coarse. The tongue often thickens. The heart beats more slowly. Weight is gained in spite of meagre meals. Constipation is frequent. Menstruation is thrown off kilter. The voice can deepen.

Proof of an underactive gland is established by blood tests that check the level of thyroid hormone and of thyroid-stimulating hormone. Thyroid hormone keeps the body running at optimum speed. A thyroid hormone deficit is reliably detected by a blood test.

Thyroid-stimulating hormone comes from the pituitary gland at the base of the brain. It stimulates production of thyroid hormone by the thyroid gland. When there is too little thyroid hormone, the level of stimulating hormone rises. If the thyroid gland cannot increase its production of thyroid hormone, the stimulating hormone continues to rise.

Blood tests that show low thyroid hormone levels and high thyroid-stimulating levels establish the diagnosis of an underactive thyroid gland hypothyroidism.

You do have some of the symptoms of a sluggish thyroid gland. However, fatigue, constipation and weight gain with limited calories are symptoms common to many diseases. Failing kidneys can produce similar findings. So can heart failure. Depression is another possible imitator of hypothyroidism. A defective pituitary gland leads to thyroid hormone deficiency.

I can’t explain your symptoms as being due to the thyroid gland if blood tests do not corroborate that diagnosis. Other conditions ought to be explored.

Q: I have been looking for answers about the venereal disease chlamydia but have not had much success. What are the characteristics of chlamydia infection? Is it life-threatening?

A: Chlamydia (clam-ID-eeuh) is one of the most common sexually transmitted infections, with more than three million infections occurring yearly in North America and more than 80 million worldwide. Young, sexually active people bear the brunt of infection. Chlamydia is rarely, if ever, life-threatening.

In females, the cervix, the necklike projection of the uterus into the vagina, is the site of infection. A vaginal discharge results. The infection can ascend into the ovarian tubes and the pelvis to produce a serious and painful infection that can leave some women infertile.

Females can be infected without any symptoms but can still become infertile through the scarring caused by the silent infection.

In males, the urethra is the chief infection site. An infection there leads to a discharge from the penis and a burning sensation when urinating.

Either of two antibiotics, azithromycin and doxycycline, is the usual treatment drug.

Q: Which of the blood pressure numbers is more important? I have always heard that the second number was the important one. A friend tells me that it is not the case.

A: Both blood pressure numbers, the first (systolic) and the second (diastolic), are important, and elevation of either constitutes high blood pressure.

Formerly, we thought that only the second number, the diastolic reading, was a cause for concern. That thinking has been discarded. Elevations of either number or of both numbers damage the heart, the kidneys, blood vessels and the eyes.n

Dr Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write to him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.

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