The clinical names for an overactive thyroid gland are hyperthyroidism (excess of the thyroid) and thyrotoxicosis (poisoning by the thyroid). The main causes of an overactive thyroid gland are:
- Graves’ Disease: an autoimmune disease where antibodies stimulate the thyroid cells to secrete excess thyroid hormone – this is the most common cause of an overactive thyroid (80%)
- toxic multinodular goitre (Plummer’s disease): this is an enlarged thyroid gland that has lumps on it that have become overactive
- toxic adenoma (single, benign , non-cancerous lump)
- thyroiditis : this is an infection or inflammation of the thyroid gland, which may temporarily cause excessive amounts of thyroid hormone. The thyroid gland will be painful and tender. It may be painful to swallow.
- over-medication of levothyroxine.
- pituitary problems: rarely, the pituitary produces too much TSH, which over-stimulates the thyroid.
- very rarely, cancer.
There are two groups of problems which can turn the thyroid into an overactive state. Firstly, there may be a control problem. This can originate right at the top of the chain of command.
The hypothalamus may produce more of the Thyrotrophin Release Hormone (TRH), thus causing overactivity in TSH production, and hence overactivity of the thyroid itself. For example, the cells responsible for TRH production may overwork, as in the case of hormone-producing cancer called an adenoma. Fortunately, not very common.
But there may be an overstimulation of these cells from the brain itself. High levels of stress from major life events can be responsible. Young adults, especially women, may be subject to this. Or the TRH producing cells become insensitive to circulating thyroid hormone and overproduce to compensate.
More commonly, the pituitary itself may start producing more TSH. This can occur as a result of a pituitary adenoma, the growth-producing the hormone in an uncontrolled fashion. There may be a genetic problem with these cells, which may escape from the proper controls and start doing their own thing. Or, they can become oversensitive to hypothalamic TRH, with the same result. Whatever the cause, the thyroid becomes over-stimulated and more thyroid hormone is produced than is required.
Most causes of overproduction of thyroid hormone, however, occur in the gland itself. The receptors which respond to TSH may over-respond and react by overproduction of the thyroid hormones. This is a condition first described by a Japanese physician, Hashimoto.
Research has shown that the body itself makes antibodies to the thyroid tissue which initially may cause overproduction of thyroid hormone, but, in time, this effect may burn itself out and then the receptors become insensitive and the thyroid production starts to become affected the other way; resulting eventually in underproduction of thyroid hormone. This problem of antibodies as a cause of illness applies not just to the thyroid, but to other organs and tissues as well.
For reasons which may not be clear, but again are sometimes the result of major traumatic life events, the thyroid producing cells simply overproduce. The thyroid may become subject to an inflammatory process – thyroiditis – which may run its course to leave the thyroid normal again, or subject perhaps, to instability between over and under-activity.
The overactive thyroid is usually enlarged and clearly visible, a condition most often seen in young women. As a whole, women are more often affected than men, usually in the younger age groups; but it may occur at any age and in either sex.
Although most people are aware of the overactive thyroid – the swollen neck and prominent eyes, obvious signs – the condition is very much less common than the underactive thyroid.
Hyperthyroidism was first described as far back as 1835, by an Irish physician, Robert Graves; and a German physician, Karl von Basedow, hastened to write a paper about it in 1840. Hence in the UK we call it Graves’ disease , and the Europeans call it Basedow’s disease.
In general, it is diagnosed without difficulty. Its treatment, however, is often not at all satisfactory. In making a diagnosis, the doctor goes by a clinical appraisal, which should follow an invariable course. They listen to the symptoms and makes an examination to determine the signs; backing this up by blood tests. Following which the treatment is decided upon. Let’s go through this in a little more detail.
The most obvious of the hyperthyroid symptoms is that the patient will appear nervous and anxious as a general rule, and indeed may be thought to be suffering from anxiety only. Most patients are losing weight in spite of a good appetite, although occasionally the patients may be anorexic. They complain of frequent and loose bowel action. They tend to be breathless and though often hyperactive, tired at the same time.
There is a usual complaint of feeling hot much of the time, always turning down the heating, and they become aware of palpitations , either because the heart beats too fast or the pulse has become irregular.
It is most important to tell the doctor ALL the symptoms you experience. Being “energetic” or “tired” isn’t enough for the doctor to make a proper diagnosis. Use the hyperthyroid signs and symptom list. It is the doctor’s job to put this all together and they can’t do this if they don’t know all of your symptoms.
Eye problems can start months before other symptoms, and carry on for a while after treatment. The whites may appear bloodshot. They may have a gritty feeling and you may have a problem with bright sunlight. The upper lids may pull upwards giving a starey appearance. You may have trouble focussing or have double vision.
In Graves’ Disease, your eyes may protrude, water a lot and the upper lids may become puffy. Bags may appear under the lower lids. The eyes might ache. Without treatment, your sight is at risk from corneal ulceration. Smoking makes matters worse so it is advisable to give up.
Hair often becomes much thinner and appears “fly-away”, with a tendency to go grey. It may not take a perm.
Your throat may be tender and feel lumpy. Swallowing can be difficult. Swelling on your neck could indicate enlargement of your thyroid gland (goitre). Because weight loss is sometimes severe, it looks as though you have a goitre but do not.
Digestive problems occur because the metabolic rate speeds up considerably. Some people feel hungry all the time and cannot understand the weight loss because they are eating more. Fat stores are burnt off first and then body tissue if the illness is not treated. Conversely, you may lose your appetite. You may also vomit. You may become very thirsty and pass a lot of urine.
Because the increase in thyroid hormones speed up metabolism , the heart beats faster. You might notice a “butterfly” feeling in your chest. Your heart may beat very fast in either a regular or irregular rhythm (palpitations). Sometimes your heart may beat so fast you will feel faint. You may also have low blood pressure.
Shortness of breath is noticed after climbing stairs, carrying heavy objects or sometimes even walking. It can happen when you experience palpitations.
You may need to go to the toilet more often but the stools are normally formed. The stools may be pale because extra fat is being rushed through the system. Some people have diarrhoea.
Your skin may become thin, soft, warm, damp and may flush easily. You may also itch. Spidery veins may appear on your cheeks. Your hands may seem red and sweaty. People with Graves’ Disease sometimes develop patches on their lower legs that are reddened and thickened (pretibial myxoedema), and the hair on the legs may be coarser. Patches may also appear on the foot or the big toe. You may also bruise more easily because the number of your platelets is reduced.
Nails appear thick and flaky. They may become loose at the nail bed, where dirt collects and the tips may rise up. The fingertips may also swell.
On-going overactivity of the thyroid gland over a long period may cause osteoporosis , which may produce aches and pains, especially in the back.
Too much thyroid hormone can speed up the breakdown of muscle fibres quicker than they can be replaced. You may feel weakness all over your body especially in the shoulders, upper arms and thighs. Your hands may be swollen and painful too. The doctor may find that you have brisk reflexes.
Metabolism increases and therefore our bodies produce excessive heat, which results in constant sweating, particularly at night which is often put down to the menopause. You may find yourself walking around in T-shirts and shorts in the middle of December, with the windows open and the central heating switched off!
Your ankles may swell. You may be given a diuretic drug used for water retention.
Patients find themselves unable to cope with life’s demands, lose their temper frequently and burst into tears for no reason. They may feel nervous, anxious and irritable, although some people feel apathetic. You may feel tired but be unable to sleep. Concentration becomes difficult. You may have racing thoughts and be very talkative. You may have mood swings. Anti-depressants are often prescribed.
You may have an increased libido (sex drive).
Your periods may be lighter than normal or even stop altogether. Periods may become irregular.
Fertility is reduced in both men and women. If you do conceive, there is an increased risk of miscarriage.
Tremor and shakiness may occur in your hands. It may be difficult to hold a cup and saucer. The tremor is obvious with outstretched hands. You may feel an inner tremor too.
Many people have surges of energy and can’t sit still for a minute. Some people are talkative, nervous and full of unnatural energy. They have to stay in bed because the huge amount of thyroid hormones has made them feel exhausted and unable to move. It’s as though the body is in a crisis – and it is!
A classic sign of hyperthyroidism in men is breast enlargement.
Weight loss may well be apparent in a number of patients, but certainly not all; there may be staring eyes, the result of the fat behind the eyes swelling partly with fluid. This is called exophthalmos.
One classic sign is lid-lag, where the doctor asks the patients to look at their finger as they rapidly drop it in front of the patient’s vision. The upper lid lags behind the eye following the finger. The pulse will be rapid, sometimes irregular, and the hand will be unexpectedly warm to the touch; obvious too, will be a tremor of the hand.
The extra blood flow to the thyroid can sometimes be picked up by the doctor through their stethoscope; they can hear a rushing noise, which is called the ‘thyroid bruit’.
The blood pressure will be revealing too: the upper (systolic) value will be unusually widely separated from the lower (diastolic) value. Another typical finding is pretibial myxoedema, a puffiness apparent over the bone of the lower leg.
Armed with all this information, the diagnosis should be clear. Confirmatory blood tests will show abnormally high T4 and/or T3 levels, and the presence of antibodies will suggest Graves’ disease.
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