Sunday 5 October 2014

Hypothyroidism, Hyperthyroidism and the Thyroid


 The thyroid gland consists of two connected lobes and is the largest endocrine gland in vertebrates. It is in common parlance said to have a butterfly shape. The thyroid gland is found below the “Adam’s apple” (the laryngeal prominence) in humans. It controls our sensitivity to other hormones, how the body makes proteins and uses energy.  The thyroid produces two main hormones thyroxine (T4) and triiodothyronine (T3). Triiodothyronine is also referred to as tetraiodothyronine, triiodo referring to 3 iodine molecules. T3 and T4 form triggers for the functioning of most other systems of the body. The main components of T3 and T4 are thyrosine and iodine. The thyroid assists calcium homeostasis by producing cacitonin. Calcium homeostasis helps maintain sufficient levels of calcium in the body.
  
Thyroid-stimulating hormone (TSH), produced by the pituitary gland triggers the thyroid to produce T3 and T4. The pituitary gland is in turn regulated by thyrotropin-releasing hormone (TRH) which is produced in the hypothalamus.
  
The thyroid gland is made-up of two lobes or wings, the left lobe referred to as  lobus sinister and the right lobe called lobus dexter. Both lobes are 3 cm wide, 5 cm long and 2 cm thick. The thyroid is located on the frontal side of the neck below the Adams apple. Occasionally there is a third lobe, the pyramidal lobe present forming part of the thyroid. This lobe is a remnant of the fetal thyroglossal duct. The thyroid gland weighs 18-60 grams in adults and even more in women during pregnancy.
  
There are two types of dysfunctions of the thyroid gland, Hypothyroidism and Hyperthyroidism. In Hypothyroidism the gland produces less than sufficient levels of thyroid hormones and in Hyperthyroidism the hormones are produced in excess.
  
Hypothyroidism
Hypothyroidism is a common thyroid disorder. The symptoms of hypothyroidism are fatigue, intolerance to cold, weight gain, inability to concentrate, dryness of the skin, hair loss and more. It may lead to delayed growth and intellectual impairment in children. It is called cretinism in extreme cases. The diagnosis of hypothyroidism is a simple blood test measuring thyroid-stimulating hormone, thyroxine and triiodothyronine. The lab range for TSH is between 0.30 to 5.5 measured in uIU/ml (international units per milliliter), the lab range for T3 is 60 – 200 ng/dl (nanogram/deciliter) and the lab range for T4 is 4.5 to 12 ug/dl (microgram/deciliter). However labs may use different measurement representations. There is however a debate in the medical community about the reference range of TSH used by testing labs for screening hypothyroid patients. It is being advocated that the upper limit be reduced from 5.5 to 3.0  uIU/ml.
  
The most common cause of hypothyroidism is deficiency of iodine in the diet. So the best preventive measure is to include iodized salt and other foods containing iodine. Hashimoto’s thyroiditis is an autoimmune disorder; it is another common cause of this thyroid syndrome. Some other causes of hypothyroidism are a thyroid surgery, malfunctioning or injured pituitary gland and the hypothalamus. There are many instances of the thyroid not functioning since birth. Hypothyroidism can be easily treated with artificially manufactured hormone supplementation. The dose is usually adjusted according to TSH and thyroxine normalization levels, taking into account clinical symptoms.
 
Deferred relaxation after the ankle jerk reflex test is a distinctive sign of hypothyroidism, other signs and symptoms are: fatigue, dry coarse skin, feeling cold, cool extremities, poor memory and concentration, Myxedema, constipation, dyspepsia, hair loss, weight gain with poor appetite, slow pulse rate, shortness of breath, swelling of the limbs, hoarse voice, delayed relaxation of tendon reflexes, heavy menstrual periods, carpal tunnel syndrome, abnormal sensations, pleural effusion, ascites, pericardial effusion, poor hearing.
  
Hyperthyroidism
Hyperthyroidism is a condition in which the thyroid gland makes excessive amounts of thyroid hormones. The condition is also referred to as hyperthyreosis or overactive thyroid. In hyperthyroidism both thyroid hormones (T3 and T4) circulating in the body are over produced. The most common cause of hyperthyroidism is Graves’ disease. Thyrotoxicosis is caused by hyperthyroidism. Thyrotoxicosis is a clinical syndrome which occurs due to extreme elevation of T3 and T4 in blood serum. However, Thyrotoxicosis may occur without hyperthyroidism and may be attributed to swelling of the thyroid gland. Thyrotoxicosis may be exogenous in nature and could happen due to accidental excessive ingestion of the prescription thyroid hormone.
  
Hyperthyroidism is a condition more difficult to manage than hypothyroidism. The management of hyperthyroidism involves the use of antithyroid drugs, suppressing the thyroid function. However, a more permanent solution is radioisotope therapy or surgery. All methods have the risk of inducing hypothyroidism. Hyperthyroidism has a high probability of being cancerous in origin.
  
Every function of the body speeds up, if there is too much thyroid hormone. Hence, some symptoms of hyperthyroidism are nervousness, vomiting, irritability, lightened menstrual flow, increased perspiration, frequent bowel movement, racing heart, hand tremors, weight loss, anxiety, difficulty sleeping, thinning of the skin, fine brittle hair, and muscular weakness.
 





 
 

No comments:

Post a Comment