Management and Monitoring Thyroid Dysfunction
Thyroid hormones are necessary for proper metabolism and growth of the human body. Except brain, testes, and spleen, all tissues experience an increase in oxygen consumption when stimulated by thyroid hormones.Thyroid hormones stimulate carbohydrate use and glucose absorption along with growth and maintenance of healthy central nervous and skeletal systems.
Hypothalamic-pituitary-thyroid axis is responsible for production and the release of thyroid hormones.Thyrotropin-releasing hormone (TRH), which is produced in the brain's hypothalamus, promotes the synthesis and release of thyroid-stimulating hormone (TSH) from the anterior pituitary. TSH then acts on the thyroid gland, to the synthesis and release of thyroid hormones T3 and T4. If T4 and T3 concentrations increase, the pituitary and the hypothalamus decreases the production of TSH and TRH, thus regulating thyroid hormone production.
Thyroid function tests is done to measure the thyroid hormones T3 and T4, as well as the measurement of TSH in blood serum. TSH is a sensitive marker, and it remains the single best indicator of thyroid function. If the TSH level is normal, primary thyroid disease is ruled out, and no further testing generally is needed. A low TSH level is an indication of hyperthyroidism, or overactive thyroid. A high TSH level suggests hypothyroidism, or underactivite thyroid .
If TSH level is abnormal,T4 and T3 levels may be measured to confirm a diagnosis of thyroid dysfunction.A free serum level is more accurate in detecting thyroid activity than a total serum level , as these are not affected by protein binding. Free T4 levels are commonly used to distinguish between hyperthyroidism and hypothyroidism.
In some cases there may have increased or decreased TSH levels but normal levels of T3 and free T4. This is called subclinical thyroid disease where the patients do not have any of the thyroid symptoms.
During treatment of thyroid disfunction, TSH levels takes a few months longer to stabilize than T3 and T4 levels. Thus transient TSH abnormalities during treatment should not be confused with subclinical thyroid disease.
Hypothyroidism is a very common disorder in which the thyroid gland fails to release sufficient amounts of thyroid hormones. The risk of hypothyroidism increases with age and is more common in females. Primary hypothyroidism,is the most common form of hypothyroidism, a problem with the thyroid gland itself. Hashimoto's thyroiditis is an autoimmune disorder, in which thyroid gland is unable to produce thyroid hormone.
Hypothyroidism can also be developed ,When patients are treated for head and neck cancer due to radiation effect as radiotherapy destroys the thyroid gland.
The dysfunction of the anterior pituitary or the hypothalamus is called Secondary hypothyroidism . Hypothyroidism due to pituitary failure is uncommon but should
be suspected in a patient with a low thyroxine level and low TSH levels.
Thyroid replacement therapy is lifelong procedure. Usually Levothyroxine sodium (T4; L-thyroxine) is recommended for the treatment of hypothyroidism because it is clinically stable, is relatively inexpensive, free of antigenicity, and has uniform potency.
The synthetic T4 is converted in the body, when needed, to the more biologically active hormone T3.It may take weeks or a month to achieve steady state in all patients.
Levothyroxine is to be taken 30 minutes prior to meals in order to avoid delayed absorption with fiber or bran in the diet.The dose is to be taken on morning empty stomach once in a day.
If you are on other medication which contain Cholestyramine resin, sucralfate, aluminum hydroxide, and ferrous sulfate ,then these medicines should not be taken within several hours of levothyroxine since these will delay the absorption of levothyroxine .
Other medicines containing carbamazepine, phenytoin, and rifampin may induce the clearance of levothyroxine; therefore, the dose of levothyroxine may need to be increased.
After few weeks of the initiation of management therapy of thyroid, TSH and T4 concentrations should be checked. Patients should continue to be checked every 6 to 8 weeks, with proper adjustments made in dosages until they are euthyroid.
Then the TSH level can be checked at 6- to 12-month intervals. The dose of levothyroxine does not fluctuate much until the age of 60 or 70, Once patients become euthyroid,. As patients age, the amount of thyroid binding and the albumin decrease, resulting in an increased amount of free, active thyroid hormones.