Successfully treating thyroid disorders is a tall order for any doctor. It’s vital that he not only knows about the gland itself, but also that he understands the entire endocrine system, including the complex workings of the various biochemical pathways.

Unfortunately, most medical students receive, at most, half a day’s worth of schooling in the complexities of the endocrine system. Small wonder that knowledgeable and expert practitioners able to meet the varying needs of thousands of patients are exceptionally thin on the ground.

The result is an epidemic of people walking around with undiagnosed thyroid disorders. The latest information indicates that thyroid problems may play a significant role in many of the 21st century’s most puzzling illnesses, such as myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) or fibromyalgia syndrome (FMS). This is all the more serious as, in some circumstances, untreated or poorly treated thyroid problems can lead to death (Neal JM, Basic Endocrinology: An Integrated Approach, Oxford: Blackwell Science, 2000).

There is much controversy in medical circles over states of hypothyroidism, in particular where patients have normal blood tests, but show the clinical signs and symptoms of hypothyroidism. These conditions are described as ‘biochemically normal but clinically hypothyroid’.

Subclinical hypothyroidism is common, especially in elderly women. The presence of this condition or of thyroid antibodies increases the risk of developing overt hypothyroidism. The risk is even greater if both are present (BMJ, 1997; 314: 1175-8).

Screening for hypothyroidism is particularly important during pregnancy since undiagnosed hypothyroidism in pregnant women may adversely affect their fetus (N Engl J Med, 1999; 341: 549-55).

One reason that hypothyroidism so often goes undetected is the common misconception that a diagnosis of clinical hypothyroidism can be made from blood tests alone. But many conditions can change the amount of circulating thyroid hormones in the blood - everything from pregnancy, dieting and kidney problems to prescription drugs and even illness.

In such patients, thyroid function tests are virtually useless (BMJ, 2000; 320: 1332-4). Especially in elderly patients, some of whom may have pituitary tumours or hypopituitarism, testing only for TSH may be inappropriate. Unless a doctor diagnoses hypothyroidism through careful clinical examination and history-taking, the diagnosis is likely to be missed (BMJ, 2000: 321: 1275-7)

In addition, when patients are taking thyroid replacement therapy, other drugs can affect the amount needed or absorbed. A study in hypothyroid women treated with thyroxine showed that when they take oestrogen therapy at the same time, the usual doses of thyroxine may be inadequate (N Engl J Med, 2001; 344: 1743-9).

ME: the link with thyroid Thyroid problems may be a culprit behind unexplained diseases such as ME/CFS and FMS. In most cases, the health problems experienced by these patients are part of a more basic and profound dysfunction, such as primary damage to the hypothalamus or pituitary gland through infection and/or some other insult. In Basic Endocrinology: An Integrative Approach, author J.M. Neal says that these different manifestations of thyroid dysfunction, especially those seen in hypothyroidism, require their own special treatment.