The lows and highs of thyroid
This hormone stimulates metabolism, and that creates symptoms that can include excess sweating, fast heart beat (fast pulse), irritability, trouble sleeping, increased appetite, bulging eyes, shakiness, increased body warmth, and non-blinking of the eyes.
Hyperthyroidism refers to an overactive thyroid gland. Hypothyroidism refers to an under-active gland. The thyroid, situated just below the voice box generally controls the rate of body metabolism. Normally one cannot see it and your doctor can barely feel it. When the gland is overactive, it is generally larger, but when under-active it may be larger or smaller.
When overactive, the gland puts out larger than normal amounts of thyroid hormone. This hormone stimulates metabolism, and that creates symptoms that can include excess sweating, fast heart beat (fast pulse), irritability, trouble sleeping, increased appetite, bulging eyes, shakiness, increased body warmth, and non-blinking of the eyes. If the symptoms persist and increase, the pulse may become irregular, the bulging eyes may get inflamed, the irritability may be poorly controlled and the patient will become weak and possibly intermittently paralyzed.
Ignoring this problem can result in severe illness. Thyroid disease often runs in families; anyone with a positive family history should be alert to the possibility and let his/her physician know about it.
When overactive, the gland puts out larger than normal amounts of thyroid hormone.
Diagnosis of hyperthyroidism takes advantage of knowing what “normal” is, and what happens when abnormality sets in. The normal happening is for TSH (from the pituitary) to vary inversely with free T4 (thyroid hormone). We can measure both of these in the blood routinely. If free T4 goes up, TSH goes down (too much thyroid hormone). If free T4 goes down, TSH goes up (too little thyroid hormone). By way of this mechanism, whatever we do from minute to minute and day to day, our bodies are able to keep our thyroids working at a normal level with very fine control.
What if I test overactive?
The thyroid is controlled normally by the pituitary gland underneath the brain. The usual case of hyperthyroidism is due to the thyroid, itself, getting out of hand. Rarely does the pituitary cause hyperthyroidism. The usual cause is a local upset in the thyroid’s immune system that results in a greater outpouring of thyroid hormone. Sometimes it is an autoimmune inflammation of the thyroid that causes it. Sometimes a benign tumor within the thyroid gets out of metabolic control. Rarely is it cancerous.
If the thyroid becomes hyperactive (overactive) and the free T4 rises, then the TSH becomes suppressed and we get a high T4 and a low TSH. The TSH value is very sensitive and is used by itself as a screening test. It would be low if someone were taking too much thyroid hormone in pill form, i.e., overdosing. In order to make an accurate diagnosis, other tests are done: free T4 and a thyroid uptake and scan.
The thyroid uptake and scan does two things: it tells you whether the gland is making thyroid hormone at a greater rate than normal, and it gives you a picture of the uptake, i.e. a picture of the gland and an idea of its size. These are important outcomes because they may rule out other causes of hyperthyroidism that would require different treatment.
Treatment of hyperthyroidism varies with the details of a patient’s history: pregnancy, childhood, medications, previous occurrence, past medical history. Treatment with medication may be symptomatic in preparing the patient for radioactive iodine treatment, or it may be definitive in suppressing the gland’s over-activity. Either way, there is no rushing the process.
Surgery may be used to remove part of the gland. This is the least used treatment these days, but under certain circumstances it may be the preferred mode of treatment. In some instances, steroids are the treatment of choice. Exactly what the physician does depends upon the details of the case.
Hypothyroidism is permanent
For the most part, hypothyroidism is permanent. Occasionally it is a transient state, and the patient will become normal without treatment. A specialist is required to make that decision.
A few years ago, a number of studies were conducted showing that follow-up in patients with treated hypothyroidism was inadequate. About 30-50% of the patients did not have adequately controlled hypothyroidism due to inadequate follow up. Once well treated, the patient should be followed up yearly with a TSH and free T4.
One has to consider adverse effects or complications of treatment. These occur in a very small percentage of cases and are usually mild and reversible, but they can be severe. The occurrence is about one percent.
Also, patients with severe eye problems related to thyroid disease (thyroid ophthalmopathy) may have to be treated specifically for the eye problem with ongoing medication while the thyroid is being treated and afterwards. Smoking aggravates this particular problem. If your doctor tells you to stop smoking, it is for your eyes’ benefit.
After successful treatment, the pulse settles down, the sweating and tremors go away, irritability returns to a usual level, but the appetite stays. Most patients have to guard against excessive weight gain.
Occasionally, a year or two after treatment ends, hyperthyroidism may recur, or hypothyroidism may arrive. All patients need to see their doctor for regular follow- ups to make sure that levels stay in the normal range.
Hypothyroidism is the other end of the spectrum from over-activity. Patients tend to become sluggish, constipated, acquire dry skin and hair, gain weight, become puffy and have aches and pains. However, a lot of overweight people who eat a lot of salt and/or sugar tend to look this way but have normal thyroids.
The laboratory comes to the rescue. The TSH is high and the free T4 is low. These are the hallmarks of hypothyroidism, but again a few more tests may be needed to confirm the diagnosis. The RAI (radioactive iodine) uptake is usually low.
The thyroid may be quite large, or not palpable, or anywhere in between. The usual cause is autoimmune thyroiditis, which is chronic and asymptomatic - and causes a moderately enlarged gland.
In this case, a failing gland is unable to put out a normal amount of free T4. That blood level falls and the pituitary reacts by putting out more TSH to stimulate the thyroid (which is unable to respond). Therefore, the result is high TSH and low free T4.
Most often this occurs slowly over many years so that no one can tell the difference from one year to the next. Sometimes only a picture from five to ten years previously shows that this look is not just the result of aging. If someone seems to have a noticeable thyroid, he/she should have it checked out - especially if there is a family history of thyroid disorders. If there is any confusion or controversy about the diagnosis or if the case is complicated, specialized help should be sought.
Hypothyroidism is treated with oral thyroid hormone, which should be started at low dosage and raised over time to maintenance. Dosage varies among individuals.
Food, medicine, herbals can interfere with treatment
Some medications interfere with thyroid hormone absorption by up to 100%.
Food taken with thyroid medications interferes with thyroid hormone absorption, and may decrease absorption by 20%.
Some medications interfere with thyroid hormone absorption by up to 100%. I once saw a woman who took a standard dose of thyroid for many years with good results but had lately become hypothyroid on the medication. Without telling her doctor, she began taking antacids regularly. When I saw her, she was distinctly hypothyroid. I had her stop the antacids, and two months later she was normal.
Some herbal medicines contain chemicals that are absorbed and interfere with thyroid hormone action in the body, thereby causing hypothyroidism.
There are all kinds of variations in details from what I have written. If your physician does something different from what you have read here, remember those details - the devil is in them.
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"The lows and highs of thyroid"
C. Robert Meloni, M.D., FACP, FACE, is board certified in both internal medicine and endocrinology. He is a graduate of Harvard College (BS), Georgetown University (MS), and New York Medical College (MD). The former Chairman and President of the Nort...