Hypothyroidism, or an underactive thyroid system, is one of the most underdiagnosed and important conditions in the United States. It has been called the "unsuspected illness" and accounts for a great number of complaints in children, adolescents and adults.
What kinds of complaints characterize an underactive thyroid system? Low energy and fatigue or tiredness, especially in the morning are frequent in these patients. Difficulty losing weight, a sensation of coldness--especially of the hands and feet, depression, slowness of thought processes, headaches, swelling of the face or fluid retention in general, dry coarse skin, brittle nails, chronic constipation, menstrual problems-such as PMS and menstrual irregularities including heavy periods, fertility problems, stiffness of joints, muscular cramps, shortness of breath on exertion and chest pain are some of the symptoms that can be seen in people with underactive thyroid systems. Be aware that a person with a low functioning thyroid doesn't have to have all of these symptoms, he may have only a few.
Function of the Thyroid Gland
Where is the thyroid located in the body and what does it do? The thyroid gland consists of two small lobes connected together. It is located in the front of the neck, just below the voice box. The thyroid gland is responsible for the speed of metabolic processes in the body and therefore affects every organ and organ system. It is the metabolic stimulator, analogous to the accelerator of a car. Normal growth requires normal thyroid functioning. When the thyroid is not functioning properly, organs become infiltrated with metabolic wastes and all functions become sluggish.
When the thyroid gland is working properly, it uses the amino acid tyrosine and iodine to make the thyroid hormone called thyroxine or T4. Thyroxine is called T4 because it contains four iodine atoms. If a person is deprived of iodine in his diet, he develops an enlarged thyroid gland, called a goiter and symptoms of an underactive thyroid or hypothyroidism.
The other important thyroid hormone is triiodothyronine or T3, which has three iodine atoms. T3 is actually the major active thyroid hormone, being much more active than T4. T4 is produced within the thyroid gland and is later converted to the active T3 outside the thyroid gland in peripheral tissues. Under certain conditions, such as stress, the thyroid gland may produce sufficient amounts of T4 to obtain normal thyroid blood tests, but its conversion to T3 may be inhibited, causing a relative insufficiency of active T3. Under this circumstance, the patient will have hypothyroid symptoms in spite of normal thyroid blood tests. As you will see, this fact results in many missed diagnoses of an underactive thyroid system.
The production and release of T4 from the thyroid gland is controlled by a hormone from the pituitary gland, which is located at the base of the brain. This hormone is called thyroid stimulating hormone or TSH. When the level of T4 in the bloodstream is low, the pituitary increases TSH production and release, which in turn stimulates the thyroid gland to produce and release more T4. The T4 then feeds back to the pituitary, reducing the secretion of TSH in a negative feedback loop. When a person has trouble making T4 due to iodine deficiency or for some other reason, one would expect to find an elevated TSH. The pituitary's TSH is trying to get the thyroid gland to produce more T4. If both T4 and TSH are low, this may indicate a pituitary problem with a low TSH secretion resulting in the low production and secretion of T4.