Thyroid is a gland which secretes a hormone to regulate the functions of our body. Sometimes its activity becomes increased more than usual and sometimes its activity is slower than usual. These abnormalities are known as hyperthyroidism and hypothyroidism. Thyroid abnormalities are more common in women than in men. Hypothyroidism increases with aging.
Hypothyroidism can be classified into different groups based on the organ responsible for the abnormality and the severity of disease, including:
– “primary hypothyroidism” (hypothyroidism due to a thyroid gland abnormality) in which there is a decreased concentration of free T4 and an elevated concentration of TSH.
– “secondary hypothyroidism” (hypothyroidism due to a pituitary gland abnormality) in which there is a decreased concentration of both free T4 and TSH (the T4 is low since there is inadequate stimulation of the thyroid gland by TSH). When the TSH and free T4 are both low then a structural lesion in or around the pituitary gland should be ruled out with a radiology test.
– “tertiary hypothyroidism” (hypothyroidism due to a hypothalamic or CNS abnormality)
– “sub clinical hypothyroidism” in which there is an elevated TSH concentration but the free T4 level is normal. Many of these women become hypothyroid eventually, and many physicians use the presence of abnormally high levels of anti-thyroid antibodies to direct their treatment. If there are elevated anti-thyroid antibodies then the patient will most likely become hypothyroid and may develop a goiter if untreated, so treatment should be considered. If there is a minimal elevation in TSH and the patient is asymptomatic with normal anti-thyroid antibody levels, then annual TSH levels to monitor the progression of disease could be considered.
The clinical appearance of hypothyroidism involves a spectrum of abnormalities from “unrecognized” to “overwhelming.” The symptoms are often mild and go unnoticed, but may include menstrual irregularity or amenorrhea, cold intolerance, constipation, decreased energy and exercise tolerance with easy fatigability and so on…
Causes for hyperthyroidism include:
– Graves’ disease (diffuse goiter),
– Plummer’s disease (nodular goiter, generally seen in postmenopausal women), and
– A pituitary TSH secreting tumor, which is a rare cause of hyperthyroidism (both the TSH and free T4 are elevated)
Graves’ disease appears to be caused by TSH like antibodies produced by an autoimmune disorder. These TSH like antibodies bind the TSH receptors to continuously activate them. These auto antibodies have been referred to by a number of names including TSI (thyroid stimulating immunoglobulin) and LATS (long acting thyroid stimulator). The diagnosis of Graves’ disease or Plummer’s disease is made by finding a suppressed TSH, an elevated free T4 or free T3, and a radioactive iodine uptake scan to indicate the presence of a diffuse goiter (Graves’), a solitary hot nodule (Plummer’s) or a hot nodule in a multinodular goiter (Plummer’s).
Up to 50% or more of patients who receive radioactive iodide treatments for an overactive thyroid, develop permanent hypothyroidism within a year of therapy. This is the standard treatment for Graves’ disease, which is the most common form of hyperthyroidism, a condition caused by excessive secretion of thyroid hormones.