Hypothyroidism refers to an endocrine disorder of the thyroid gland in which it secretes the thyroid hormone to the blood circulation in deficient quantities. In this article, there will be a discussion of the causes of this disorder in addition to the medical symptoms and the possible treatments. The thyroid gland is situated in the anterior part of the neck and is specialized for the secretion of of three hormones. Two of them are derivatives of each other. These hormones are: Thyroxine and triiodothyronine. The other hormone is called calcitonin and is synthesized and secreted by specialized cells of the thyroid gland which are called parafollicular cells.
This hormone has an important function in the homeostasis of calcium ions in the blood. This hormone is not involved in the condition which is called hypothyroidism. The other two hormones which are secreted by the thyroid gland are derivatives of each other by a modification of one iodine atom.
Thyroid hormone is the main hormone that is affected in the condition that is called hypothyroidism. This hormone requires iodine atom for its biosynthesis in the thyroid cells. This iodine atom must be supplied in the diet. Otherwise goiter can develop which is an enlargement of the thyroid gland. This condition can occur due to the deficient amount of iodine that is required for the normal function of the thyroid hormone.
The thyroid hormone in both forms thyroxine and triiodothyronine is required for the proper functioning and growing of the body tissues. It is required for the metabolic processes in the body. This hormone stimulates the increase in matabolic rates in the bodyby increasing the sythesis of proteins. In addition, it has a general effect on all body tissues promoting all types of metabolic functions in the body.
The thyroid hormone is derived from the amino acid tyrosine by biochemical conversions which occur in the thyroid cells. The thyroid hormone has a hydrophobic structure that can penetrate the cellular membrane of target tissues readily causing its effect by binding to nuclear receptors inside the nucleus of the cell, thus increasing the rate of proteins translation on the cellular ribosomes. For all these important functions of the thyroid hormone we can understand the importance of constant supply of this hormone to the body tissues. Therefore, disorders which involve the thyroid hormone are manifested clinically by many symptoms that can affect the whole body.
Thyroid hormone is similar in its physiological effect on the body to the hormones epinephrine and norepinephrine in the sense that it increases the metabolic rate in the body in general. In addition, it induces symptoms that are triggered usually by the effect of epinephrine and norepinphrine on the body such as increased heart rate.
Hypothyroidism can be caused due to several reasons. One of them is surgical procedure to remove part of a hyperactive thyroid gland. One complication of such a procedure is the development of hypothyroidism in the affected individuals. Also treatment of hyperactive thyroid gland with radioiodine can lead to the same result as with surgery. A side effect to these two procedures is the development of hypothyroidism. The main cause of hypothyroidism is however an autoimmune destruction of the thyroid gland by circulating antibodies in the blood which recognize the thyroid tissue as foreign, thus causing its destruction.
In the case of hypothyroidism the level of the thyrod hormone in the blood is low. As a result the pituitary gland starts to synthesize and secrete more of the thyroid stimulating hormone (TSH) to the blood circulation, thus one manifestation of hypothyroidism is elevated level of the TSH in the blood of affected individuals. Actually the detection of high blood level of this hormone can be an indication of hypothyroidism. this is in addition to the other possible condition of pituitary gland oversecretion of this hormone due to an adenoma or a tumour that affects this gland.
The symptoms of this disorder are directly related to the absence or deficiency of the thyroid hormone in the blood. One such prominent symptom is the development of constipation in the affected individuals due to the sluggish metablic rate in these patients, thus the gastrointestinal motility in these patients is slower than usual. The treatment of this disorder is to administer supplementary amount of the thyrroid hormone in order to reverse the symptoms.