DEAR DR. DONOHUE: I am a man, age 54, who has had high blood pressure for two years. I have taken umpteen different blood pressure medicines in varying amounts, but I cannot get my blood pressure down to where it should be. My doctor mentioned I might have a narrowed kidney artery, and he wants me to undergo tests. What is this all about? – W.K.

ANSWER: The kidney plays a pivotal role in regulating blood pressure. When it detects a blood pressure drop, it releases a substance called renin that is involved in the production of a powerful product that raises blood pressure.

If an artery to one kidney (or sometimes arteries to both) is constricted, blood pressure to that kidney is on the low side, and the kidney is fooled into thinking the whole body has low blood pressure. It constantly releases renin, and blood pressure stays elevated. This kind of blood pressure can be difficult to control with medicine. It is called renovascular hypertension – “reno” for the kidney, and “vascular” for the narrowed artery.

In a way, this kind of high blood pressure is not all that bad. It is potentially curable.

In the same manner that clogged heart arteries are opened with a balloon-tipped catheter, the narrow kidney artery can be opened. Once normal flow is established, the kidney stops its production of renin.

Surgery is another way of correcting the problem.

When circumstances prohibit the use of these invasive procedures, people must depend on medicines to combat their renovascular high blood pressure.

Special scans and X-rays establish the diagnosis of kidney artery narrowing.

There are many variations on the above theme. The sketchy outline I have provided does not include all the varieties of renovascular high blood pressure.

DEAR DR. DONOHUE: For the past 10 years I have taken monthly B-12 shots for pernicious anemia. I am getting tired of shots. Can’t I take the vitamin in tablet form? I like my doctor, but I don’t like seeing him so often. – R.Z.

ANSWER: Pernicious anemia is the result of vitamin B-12 deficiency. It’s not that you or others don’t get enough of the vitamin. It happens because your digestive tracts cannot absorb it.

For vitamin B-12 absorption, people must have intrinsic factor, a substance made in the stomach. It ferries B-12 across the digestive tract into the blood and eventually into the bone marrow, where blood cells are made. Without the vitamin and intrinsic factor, red blood cell production falters.

Injections of B-12 bypass the intrinsic factor problem. The vitamin has no trouble entering the blood vessels in muscles. From there it can then be transported to the marrow, where it does its work.

Some European doctors treat their pernicious anemia patients with massive doses of the vitamin. When given in large amounts, enough B-12 can pass through the digestive tract wall and make it to the bloodstream. Not too many doctors in North America employ this method.

B-12 is available as a nasal preparation. Ask your doctor if you are a suitable candidate for it. That can eliminate shots. The shot, however, is a proven and reliable form of treatment.

DEAR DR. DONOHUE: Two months ago my husband suffered a heart attack. He is 47. He is back to work and doing as much as he did before the heart attack, except for sex. His doctor said it was OK for us to have sex, but he has it in his mind that this is too much of a strain on his heart. Can you set the record straight? – C.K.

ANSWER: The chance for intercourse precipitating another heart attack is all but nonexistent. It is not that much of a strain on the heart. It is in the same league with climbing stairs, raking leaves or ballroom dancing.

If your husband remains unconvinced, have him ask his doctor for a stress test. That can quantitate what degree and amount of exercise he can safely endure. Many people are permitted to resume weightlifting after they have recovered from a heart attack.

DEAR DR. DONOHUE: I have four children. Three are girls and the fourth, only 2 months old, is a boy.

My husband wants the boy circumcised. I am not for it. He says leaving the boy uncircumcised will make him feel different from other boys. Can you furnish any other justification for it? – R.R.

ANSWER: Circumcision became a common practice in North America because of an intense program to promote hygiene. Hygiene is not a strong argument for circumcision. Almost all uncircumcised men can retract the foreskin and practice cleanliness as well as circumcised men do.

Some have championed circumcision as a preventive step against penile cancer. That’s not a strong argument for the practice, either. Such cancers are rare in circumcised and uncircumcised men.

Perhaps a slightly stronger argument can be made for prevention of genital warts. It’s said that circumcised men are less likely to catch such warts. The warts are due to the papillomavirus, and some papillomaviruses cause cancer of the cervix. This argument holds that a man’s partner benefits from circumcision. Proof of this is not overwhelming.

Circumcised boys up to the age of 5 have fewer urinary tract infections than do uncircumcised boys. Only if a young boy had repeated urinary tract infections would circumcision be of value.

In most cases, there is no advantage to circumcision. Even your husband’s argument that circumcision makes men less self-conscious is not a convincing one. More and more parents are not having their sons circumcised.

Unless it is a matter of religious or ethnic conviction, circumcision need not be routinely practiced.

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