Sunday, March 10, 2002		Fitness

Thyroid disorders can be missed in early stages
B.K. Sharma

THYROID is one of the endocrine glands along with pituitary, para-thyroids, adrenals, gonads (testis and ovaries) and pancreatic islets (producing insulin). The brain through its hypothalamus has further control over the pituitary. The word endocrine was coined by the famous physiologist, Starling, for those glands which pour their secretions directly into the blood and not into the duct or lumen of an organ.

The products of these organs are known as hormones which in Greek means "to set in motion" and this is an appropriate description of these chemicals because they set in motion their important cellular and physiological processes and their secretions are controlled by a feedback mechanism of the glands.

The thyroid is a butterfly or shield (thyreos) shaped organ located in the neck in front of the wind-pipe just above the niche of the sternum. It consists of two main lobes and weighs 12-20 gm in adult. Incidentally the para-thyroid glands which regulate the calcium metabolism are located at the back of the thyroid gland. The thyroid gland also contains certain special cells which produce the hormone calcitonin which lowers the calcium level. This entire complex therefore secretes a number of hormones. The synthesis of thyroid hormone starts during early fetal life, somewhere between the tenth to eleventh weeks of gestation and is very important for the genesis of various organs, particularly the brain. Roughly in 1:3000 infants the thyroid may not be working normally at birth and unless this is recognised early enough it can produce severe handicap in mental development resulting in a condition called cretinism.

Thyroid produces basically two hormones, thyroxin (T4) and trioidothyronine (T3) under the influence of thyroid stimulating hormone (TSH) of the pituitary which in turn is influenced by hypothalamic hormone from the brain. Nature has established almost a perfect method to regulate the amount of hormones to be secreted by the thyroid. The moment the level of hormones goes beyond the required amount, the feedback to the pituitary gland shots up the production of TSH which in turn stops or slows the production of thyroid hormones. Only in disease conditions is this system upset. The thyroid hormone plays a critical role in cell differentiation during development of the foetus and in the post-natal life it regulates metabolic homeostasis of the body as well as maintains the temperature levels. Iodine is the most critical ingredient required for the synthesis of thyroid hormone and hence the importance of adequate amount of iodine intake.

There are three main functional disorders of the thyroid which are fairly common in our country. The public is familiar with the well known and publicised iodine deficiency goitre (swelling in front of the neck due to enlargement of thyroid). This used to be a common disorder in hill areas since the low iodine content of the water in the sub-Himalayan region, eastern UP, Mizoram, delta areas and river ravines is low. An outstanding work was done on the subject by late Dr Ramalingamswamy of the All-India Institute of Medical Sciences, New Delhi. An average of 150-200 mgm of iodine is required by an adult, 100 mgm by a child and somewhere 300 mgm during pregnancy. The adequate iodine intake is ensured by the use of iodinised salt which should have at least 15 mgs of iodine content per kilogram at the consumption level. Although the problem has not been totally eradicated, but the incidence of goiter has visibly come down after the adoption of this measure.

If the iodine deficiency goes on for a long time in addition to the enlargement of the thyroid gland in the form of goiter, the function of the thyroid may also suffer and lead to low thyroid functioning or hypothyroidism. Paradoxically, excessive intake of iodine may also result in a similar condition.

This condition is found more often in women than in men and can be missed in its early stages because of its very insidious onset with symptoms which can simulate many other diseases. The symptoms may be gain in weight, tiredness, fatigue, hair loss and dry skin, feeling excessive cold, lack of concentration, constipation, hoarse voice, mild swelling of the feet and legs, rather puffy looking face, heavy lower eye lids, impaired hearing, pain in the wrist due to compression of nerves and menstrual irregularities in women.

The condition can be caused by various pathological processes of autoimmune nature (body’s own cells attacking the glands). But this may also result from surgery, treatment with radioactive iodine, low or very high uptake of iodine, drugs like lithium, amiodorone and excessive use of antithyroid drugs. Various disorders infiltrating the thyroid can do the same. If the thyroid is unable to work properly because of lack of hormone from the pituitary or hypothalamus, this is known as a secondary hypothyroidism meaning thereby that its cause lies outside the thyroid. Hypothyroidism may be associated with other diseases like diabetes mellitus, Addison’s disease, pernicious anemia, rheumato-arthritis and physicians should be very alert to these possibilities.

Diagnosis has become easy and reliable. All the thyroid hormones can be measured now and anatomically thyroid can be seen through scan, biopsy and measurement of various antibodies which may be the cause of the disease. The treatment is relatively simple and the thyroid hormone— thyroxin — can be replaced. The treatment is mostly life-long unless the cause can be removed.

Here the thyroid is working over time with the thyroid producing more hormones than required and this production is no longer under the control of the pituitary. In fact, the thyroid stimulating hormone of the pituitary levels is very low and under stimulus of various kinds (mostly autoimmune) the hormone production is fast and relentless. As can be expected, the symptoms will be opposite to hypothyrodism. Here the various metabolic processes are working over time and the person is burning his energy excessively and thus exhausting the body stores. There is loss of weight, increased appetite, higher activity, irritability, heat intolerance, excessive sweating, palpitation, fatigue and weakness. There may be diarrhoea, excessive urination and menstrual disorders. Symptoms may also include tremors of the hands, warm and moist skin, weakness of the muscles, prominent eyes (ex-opthalmos). Hyperthyroidism may also result from various autoimmune disturbances, toxic nodular goiter and the secondary hyper thyroidism due to excessive secretion of thyroid stimulating hormone of the pituitary.

There may be irregularity of the pulse, particularly in elderly persons and the patient may thus exhibit cardiac symptoms for the first time. He may go to the opthalmologist for the eye problem. The diagnosis can again be made by measurement of various hormones and the treatment can be carried out with the drugs which may be required from a few months to two years depending upon the individual patient’s condition. Surgery may be required or thyroid may be destroyed by radioactive iodine administration in which case the thyroxin hormone may have to be replaced for as long as the patient lives.

All the three common diseases of the thyroid mentioned above when seen in their advanced stages can be diagnosed by a medical student readily. But it is not easy during the early stages of both hypo and hyper thyroidism. One has seen patients often wrongly diagnosed as suffering from depression, anemia, kidney diseases, heart diseases and some time even hysteria. It is more for the physicians and the endocrinologists to consciously keep this in mind while seeing a patient with vague and non-specific symptoms and not to ignore the patient as a neurotic or hysterical.

In fact once a diagnosis is made on clinical basis or measurement of hormones every thing fits in and the response to the treatment is indeed very rewarding both for the patient as well as the doctor. On the part of the patient the consistent taking of drugs and follow-up is required because treatment is very often life long and needs continuous monitoring and prevention of various complications.