Managing thyroid troubles – includes related information
A well-functioning thyroid gland is essential for normal growth and development. It produces iodine-containing hormones that help to regulate the body’s growth, function and metabolism. Thyroid disease, especially hypothyroidism or thyroid deficiency, is a fairly common disorder, estimated to affect almost seven million North Americans. Thyroid disorders may arise through changes within the gland’s structure such as nodules or rumours, enlargement or abnormalities in its hormone output. Some thyroid disorders, such as Graves’ and Hashimoto’s disease, are autoimmune disorders where the body mistakenly regards its own tissues as “foreign” and produces antibodies against them.
What the thyroid gland does
The thyroid gland is part of the body’s endocrine system, which produces and releases hormones – biochemical messengers that target specific organs and tissues. In order for the body to maintain a healthy metabolism, the thyroid must release the right amount of hormones into the blood at the right time. If there is too much or too little, things can go wrong.
The thyroid gland makes and secretes two major iodinecontaining hormones thyroxine or tetraiodothyronine (T4) and triiodothyronine (T3) which act on specific target cells or organs and are carried around in the bloodstream bound to certain proteins. The thyroid hormones act as cell accelerators that speed up the body’s metabolic rate – its rate of oxygen use and energy production. Thyroxine (T4) increases the rate at which fats and carbohydrates are used by tissues, helps to control body temperature, influences the heart-rate and helps to regulate protein synthesis. (But T3 is the active form, and in order to exert its effect T4 is convened to T3 in the body’s cells.)
Feedback system monitors thyroid hormone levels
The balance of thyroid hormones in blood is constantly adjusted by a feedback process similar to the thermostatic control of room temperature. The rate at which the thyroid gland produces its hormones is regulated by a thyroidstimulating hormone (TSH) – secreted by the pituitary gland in the floor of the brain. And TSH production is in tum controlled by yet another hormone, thyrotropin-releasinghormone (TRH), from the hypothalamus, within the brain. Once a certain level of circulating thyroid hormones is reached, the pituitary’s TSH production drops, shutting off thyroid hormone release, to achieve the right balance. If the level of thyroid hormone in blood drops, the pituitary gland releases more TSH, stimulating the thyroid gland to secrete more hormone.
Too much or too little thyroid hormone undermines health
Prompt detection and treatment of both hypo- and hyperthyroidism are needed to prevent serious consequences. Left untreated, either form can cause health problems. With an underproductive thyroid gland, the body is short of thyroid hormones and cellular processes slow down, leading to hypothyroidism. In hypothyroidism, as the thyroxine (T4) level in blood drops, more TSH is released, triggering the thyroid to make more hormone, perhaps enlarging it and producing a visibly bulging, painless swelling or “goitre” in the lower front of the throat.
By contrast, when thyroid hormones are overproduced, the opposite, less common and less manageable problem hyperthyroidism – arises where the body’s metabolic rate can leap 60 to 100 per cent. An over-stimulated thyroid gland may also enlarge to form a goitre, can cause serious eye problems, heart failure, mental impairment, personality changes or a lifethreatening “thyroid storm.”
Tests for thyroid function
In the past, thyroid dysfunction wasn’t easily diagnosed until an advanced stage, but now simple blood tests can detect it earlier, often before symptoms appear. A suspicion of thyroid dysfunction is followed by measurement of pituitary TSH output, and when necessary, blood levels of thyroid hormones, anti-thyroid antibodies and uptake of radioactive iodine to confirm the diagnosis. Modern experts rely on the new, ultrasensitive TSH assay, which determines the amount of thyroidstimulating hormone in blood, as a marker for thyroid function. A high TSH indicates a low thyroid output – possibly subcliniCal or mild hypothyroidism – even if T4 and other tests suggest normal thyroid function. Low or undetectable TSH levels and high T4 readings suggest hyperthyroidism. Thyroid structure may be examined by a radionucleotide uptake scan or ultrasound which can reveal nodules and other abnormalities.
Hypothyroidism – too little thyroid hormone
A low thyroid output or hypothyroidism affects about one per cent of adults – many more women than men – its prevalence rising to 10 per cent or more among the elderly. Its onset can be insidious and mild cases may have subtle, barely noticed symptoms. Only about half are diagnosed while the disorder is in a mild stage. The rest may feel tired and lethargic through lack of thyroid hormones, attributing their discomfort to aging or the stress of modern life.
Those low in thyroid hormone generally feel slow, sluggish and perpetually fatigued. Hypothyroidism slows down the body ‘s metabolism and leads to a host of symptoms such as: apathy, weight gain (despite a poor appetite), slowed heart beat, constipation, depressed mood, inability to concentrate, elevated cholesterol, anemia, headache, dizziness, swollen ankles, brittle nails, dry skin and a bloated face. Some hypothyroid people have noticeably slow speech, can’t stand the cold, lose their hair, develop coarse, dry skin and a goitre. Advanced or extreme forms of hypothyroidism, known as myxedema, may produce aching muscles, a weak pulse, cool skin and a hoarse voice.
Causes of hypothyroidism include autoimmune thyroid disorders such as Hashimoto’s disease; surgery or radioiodine treatment for previous thyroid disorders (which usually result in hypothyroidism and an underactive gland); head or neck surgery or irradiation (for cancer); pituitary turnours (rare); certain drugs (such as lithium) and newborn thyroid defects.
Congenital newborn hypothyroidism occurs in about one per 4,000 newborns, making it the commonest endocrine cause of mental retardation. Delayed diagnosis and failure to treat within three months of birth lead to irreversible mental retardation, formerly called “cretinism.” Infants born with this defect need lifelong thyroxine treatment to prevent mental retardation, delayed growth, facial deformity and other consequences. Early hints of hypothyroidism include a large tongue, puffy face, dry or yellow-tinged skin, feeding difficulties, hoarse cry and failure to thrive. Owing to the seriousness of this disorder, in Canada all newborns are now screened within 3-5 days of birth for congenital hypothyroidism and prompt hormone replacement, started by one month of age, has virtually eradicated the disorder. The Canadian Task Force on the Periodic Health Examination suggests that newborns born prematurely or at home, or those discharged early, be tested for hypothyroidism within a week of birth (usually by a heel-prick blood test). In iodine-poor countries, where neonates are not screened or treated, cretinism remains widespread.
Older children and adolescents low in thyroid hormone may experience learning and other reversible problems – alleviated by hormone therapy.
Hypothyroidism is easily treatable
Whatever its causes, hypothyroidism can be simply and cheaply reversed by hormone replacement with synthetic products identical to the body’s own – generally levothyroxine, taken once a day, which has largely supplanted the desiccated thyroid (animal) extracts formerly used. Hormone replacement is geared to individual needs and those taking thyroxine should adhere to the regime, which may be lifelong, in order to maintain improvement. Symptoms gradually disappear. Even in the severely hypothyroid, a few months of treatment usually relieves the dry skin, brittle nails, tiredness and other symptoms, reviving energy and improving looks. But even when feeling better, patients should continue the hormone pills as prescribed because if they stop too soon, or without medical advice, symptoms may return in a few weeks. In the elderly and those with cardiac problems, hormone doses are kept low, as too much can trigger heart failure.
There is considerable debate as to the merits of treating people with subclinical hypothyroidism – those without symptoms, in whom thyroid hormone output is modestly depleted, where the condition is detected only by elevated TSH levels. Although thyroxine therapy is relatively safe, treatment may be lifelong. On the other hand, subclinical hypothyroidism may predispose to lipid (blood-cholesterol) abnormalities and heart disease, therefore warranting correction. Before the sensitive TSH blood test came in, some people were given thyroxine doses now known to be excessive. But nowadays, patients are monitored regularly to assess hormone levels and compliance, avoiding under- or over-treatment.
Thyroiditis describes inflammation of the thyroid gland and consequent depletion of thyroid hormones. Some types of thyroiditis involve an initial hyperthyroid (overactive) phase followed by a hypothyroid (underactive) phase. Forms of thyroiditis include:
* Chronic autoimmune (Hashimoto’s) thyroiditis, often with a large goitre, a condition that runs in families, affecting about four per cent of the population. Treatment is with thyroxine.
* “Painful” or viral thyroiditis – also called subacute thyroiditis or de Quervain’s disease – often follows a viral respiratory illness, producing an enlarged, tender thyroid, perhaps with accompanying neck and ear pain and a high fever. Viral thyroiditis, which is usually self-resolving, occurs in sporadic epidemics. Treatment is with analgesics (such as ASA or acetaminophen), plus corticosteroids to reduce severe or lingering inflammation. Thyroid-function generally returns to normal within 6-18 months.
* Postpartum thyroiditis – following childbirth – is more common than once imagined and affects about five per cent of childbearing women. Postpartum thyoiditis seems to unmask a latent but self-limiting autoimmunity, most episodes disappearing spontaneously 6-12 months after delivery. It usually involves a brief period of hyperthyroidism, followed by a bout of hypothyroidism. The condition may appear two to four months after delivery – with mothers feeling edgy and irritable, experiencing palpitations and sweating. The hyperthyroid phase may last four months or so, followed by hypothyroid lethargy, weight gain, depression and coldintolerance. While the disorder usually vanishes within a few months, a small goitre may remain. Women who have one bout of post-pregnancy thyroid trouble usually have repeat episodes after subsequent births. Treatment of postpartum thyroiditis is with propranolol to calm the heart during the hyperthyroid phase, followed by hormone replacement for the temporary period (6-12 months) of hypothyroidism.
Hyperthyroidism – too much thyroid hormone.
Hyperthyroidism, due to excess thyroid hormone, affects mainly women aged 20-45. People with an overactive thyroid gland seem restlessly energetic, have an accelerated metabolic rate, lose weight despite a large food intake, may also have an increased respiration rate and pant or perspire with the least exertion. Excess thyroid hormone can affect the nervous system, making people anxious, jumpy, irritable and generally “hyper,” sometimes also producing a rapid heart rate and palpitations. Robert Graves, the 19th-century Irish physician who described hyperthyroidism, was struck by its cardiac manifestations which can include a disconcertingly strong heart beat, irregular heart rhythms and sometimes heart failure. In extreme cases, hyperthyroidism can result in seizures and mental illness.
Different causes of hyperthyroidism
* Graves’ disease – the commonest form of hyperthyroidism – affects mainly people under age 40.
* Toxic multinodular goitre – an enlarged, benign thyroid – is more common in the over-50s.
* Pituitary tumours – which increase TSH production (rare). Medications such as amiodarone (an antiarrhythmic heart drug containing iodine) can induce hyperthyroidism.
* Excess iodine ingestion, as in those who eat large amounts of kelp (seaweed) or live in very iodine-rich areas.
* “Hamburger” disease or epidemic hyperthyroidism – due to the consumption of thyroid tissue accidentally ground up in hamburger meat and sausages – is occasionally reported.
Hyperthyroid problems may be treated with:
* Antithyroid medications, such as propylthiouracil and methimazole, relatively safe and effective drugs, although it may take some weeks until thyroid hormone levels revert to normal. Most of those taking antithyroid medications stay on them for a year or so (not longer owing to possible long-term side effects). Thereafter, some go into permanent remission, requiring no further treatment, but many relapse once the antithyroid medication is stopped. Adverse drug effects are rare, but some people on these medications develop gastric upsets and allergies. A rare but serious side effect is a decreased white blood-cell count, perhaps signalled by a severe sore throat. If this happens, the thyroid sufferer must stop the drug immediately. Other therapies may be used after antithyroid drugs.
* Radioactive iodine therapy – to shrink the thyroid gland and decrease the amount of hormone secreted – means taking a tiny amount of radioiodine as a liquid or capsule, usually after drugs have rendered the person euthyroid or back to normal hormone outputs. (Antithyroid drugs are generally given before radioiodine therapy, to reduce the chance of worsening eye and other problems.) The radioactive iodine is absorbed only by the thyroid gland, leaving non-thyroid cells unharmed. Radioiodine therapy has proven safe and effective, able to alleviate Graves’ disease in 90 percent of cases. Following the procedure, people almost always become hypothyroid and need hormone replacement-
safer therapy than trying to suppress an overactive thyroid gland.
* Thyroid surgery – partial removal of the thyroid gland generally after a period on antithyroid drugs, is occasionally but not often done any more. It still has a place for those with very large, cosmetically unattractive goitres, in whom the mount of radioactive iodine needed would be dangerously high, or if cancer is suspected and for those who prefer surgery to taking radioactive substances.
Thyroid nodules and thyroid cancer
Sometimes the thyroid gland develops small, painless lumps or nodules, often discovered during a medical examination. About five per cent of North American adults have palpable (easily felt) thyroid lumps – again, more frequently women than men. Although the overwhelming majority of nodules are benign variants of normal, some five to 10 percent are malignant and need surgical removal.
A thyroid nodule may be malignant if:
* it’s in a child, adolescent or male (thyroid nodules are less common in these groups, thus more likely to be malignant);
* it occurs after head and neck irradiation (a formerly popular treatment for acne, enlarged tonsils, adenoids or a large newborn thymus, halted in the 1960s);
* the nodule expands rapidly;
* it’s in someone under age 20.
Clinicians must differentiate between cancerous nodules and those that are benign and may respond to conservative, nonsurgical management. In the past, many nodules were removed because there was no way to tell which were malignant. But in the last 20 years several new techniques such as ultrasound, radioisotope imaging and needle biopsy have improved the diagnosis of thyroid cancer. Fine needle aspiration biopsy (FNAB) is an innovation partly pioneered by University of Toronto researchers, that has now become standard practice for diagnosing thyroid cancer. A very fine needle is put into the suspicious nodule to obtain cells for direct examination. The combination of radioisotope imaging and FNAB has considerably improved thyroid nodule diagnosis, making it is more likely that a thyroid malignancy will be detected and less likely that a benign nodule will be needlessly removed. However, in some cases – for example, a very large goitre or one that impinges on the voice-box or windpipe – a benign nodule may also be removed. Thyroid cancer is treated by radioiodine therapy and/or surgery. On a final reassuring note: although some uncommon types of thyroid cancer are highly lethal, death from a thyroid malignancy is extremely rare. Most people treated for thyroid cancer regain normal life expectancy.
Signs and symptoms of thyroid disease
Hypothyroidism (underactive thyroid)
* low energy, constant tiredness
* weight gain – despite diminished appetite
* intolerance to cold
* inability to concentrate, memory lapses
* slowed head rate
* raised blood cholesterol
* muscle weakness, cramps
* menstrual irregularities
* ankle swelling
* hair loss (especially eyebrows)
* dry scaly skin, brittle nails
* hoarse voice
Hyperthyroidism (overactive thyroid)
* mood swings, emotional instability
* mental impairment, memory lapses, diminished
* skin itching, rashes
* nervous agitation, restlessness
* hot skin, sweating
* fast, pounding head beat, palpitations
* weight loss (despite heady appetite)
* fine hand tremor
* scanty menstrual flow
* bulging eyes, an unblinking stare
* if severe, seizures, mental illness and psychosis (rare)
* in children – retarded growth, delayed sexual maturation,
The thyroid gland needs iodine: millions deficient worldwide
In order to produce its hormones, the thyroid gland must obtain at least a trace of iodine each day. Iodine deficiency during early childhood can lead to delayed development, goitre and possible mental retardation. Good natural sources of iodine are fish and other seafood, but some inland areas are low in iodine, including the Great Lakes region – formerly called the “goitre belt” – where thyroiddeficiency problems used to be widespread. To offset iodine deficiency, table salt is now iodized in North America. However, many developing and other countries still don’t iodize salt, and millions around the world have thyroid disorders that cause mental retardation through iodine lack. Agencies such as the World Health Organization list thyroid problems as one of the world’s most pressing health concerns.
Thyroid troubles afflict mostly women
Although thyroid disorders can occur in both sexes, they are five to 10 times more frequent in women than men. Hypothyroidism is a particular problem in postmenopausal women – one reason why physicians watch for this disorder and do blood tests if necessary to test thyroid function. Hyperthyroidism is similarly more common in women, especially during their 30s to 40s. The reason for the increased prevalence of thyroid troubles in women is unknown. Other autoimmune disorders where the body forms antibodies against its own tissues are also more common in women – for example pernicious anemia, rheumatoid arthritis and insulin-dependent diabetes.
Hypothyroidism in the elderly often dismissed as senility
In older people, a hypothyroid state may begin with vague changes such as fatigue, dry skin, brittle nails, thinning hair, often wrongly attributed to normal aging. The depression and lassitude that accompany hypothyroidism – which would likely be investigated in younger people – may be taken for senility in the elderly and left untreated. In one study, eight per cent of patients complaining of malaise were labelled ,’depressive” but later found to be suffering from undetected hypothyroidism. Hormone treatment greatly improved their wellbeing. Most doctors now watch for the condition in the elderly.
Graves’ disease is an autoimmune disorder in which the body produces antibodies that lead to thyroid over-stimulation and hormone over| production, sometimes three to four times above normal amounts. Although not invariably present, a goitre or enlarged thyroid is a classic sign of the disease. Graves’ disease may also be accompanied by bulging eyes, retraction of the eyelids and a staring “pop-eyed” look known as exophthalmos. The eye complications can be severe, producing double vision. Whether Graves’ disease and exophthalmos are both manifestations of the same underlying autoimumune disease, or whether they ate closely related but different disorders, remains debatable. Mild eye problems are dealt with symptomatically, using lubricating eye drops, eye patches at night, or raising the head of the bed to prevent fluid accumulation. Severe cases may require immunosuppressants to reduce inflammation. Very severe cases may need eye surgery.
During pregnancy, Graves, disease may remit spontaneously – a result of the autoimmune suppression which often occurs in pregnancy, so that a woman’s body won’t reject the fetus as “foreign” – but it tends to recur following the birth.
COPYRIGHT 1994 Strategic Inc. Communications Ltd.
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