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Primary and Secondary Hypothyroid Disorders

Direct and Indirect Causes of an Underactive Thyroid Gland

Aug 21, 2009 Jim Lowrance

Most cases of hypothyroidism are due to problems within the thyroid but there are other causes that indirectly cause under-functioning of the gland.

Thyroid disease is a primary cause of hypothyroidism, meaning it is a problem within the thyroid gland itself. Secondary causes of hypothyroidism would be those that do not originate within the gland but are other problems within the body that indirectly affect thyroid hormone levels.

Primary Causes

Thyroid autoimmunity - is an immune system response, in which auto-antibodies are created to attack thyroid proteins and is the most common cause of hypothyroidism in industrialized countries. In addition to causing destruction of thyroid tissue over time that, results in the gland under-functioning, normal thyroid tissue is also taken over by abnormal tissue that can no longer absorb iodine from things in the diet, to produce thyroid hormone from. This includes development of thyroid nodules (small tumors) that also take up space within the gland, so that there is less normal tissue for normal thyroid functioning.

Other primary causes – include injuries to the thyroid gland that diminish its ability to function normally and glands that are not fully developed at birth or following birth. If for example, a person is in a severe car accident that causes trauma to the throat, the thyroid gland can be directly damaged and once this occurs, any resulting hypothyroidism would be a problem within the gland. People who are born with only partial thyroid glands or small inadequate ones that do not develop as they become adults, can experience hypothyroidism which would also be a problem originating within the gland itself.

Secondary Causes

Biochemical hypothyroidism – are cases in which a chemical element needed by the thyroid gland is lacking or the gland is damaged by a drug or other chemical that is harmful to the body or hinders thyroid function. Iodine deficiency is in this category and occurs when there is inadequate iodine consumed in the diet. The thyroid is highly dependent on this chemical element that is used by the gland to produce hormones that regulate metabolism and so iodine deficiency causes the thyroid to hypo-function. An example of chemical damage to the thyroid and resulting hypothyroidism would be when drinking water has been contaminated with radioactive chemicals and results in cell destruction within the gland.

Failure of major endocrine brain glands – is a condition often referred to as “Central Hypothyroidism”, meaning the brain-center is failing to regulate the thyroid gland. The two master glands that stimulate the thyroid to operate at normal levels are the hypothalamus and pituitary glands. The hypothalamus sends TRH (thyrotrophin releasing hormone) to the pituitary gland, which in turn sends TSH (thyroid stimulating hormone), also called “thyrotrophin” to the thyroid gland, which completes the process by supplying the body with thyroid hormones. A failure on the part of either master gland, due to tumors within them or disease processes affecting them, results in secondary/central hypothyroidism.

Other secondary causes – include women who develop under-functioning thyroid glands as a result of pregnancy, also referred to as “postpartum hypothyroidism”. Certain types of diseases can also affect thyroid function, including those affecting other glands in the endocrine system (hormone producing). Chronic stress and severe emotional disorders can cause the T3 thyroid hormone specifically to become low. This less-common condition is referred to as “Euthyroid Sick Syndrome” or “low T3 Syndrome” and is a secondary cause that usually only requires short term treatment.

Patients who are diagnosed with hypothyroidism should request that their doctors inform them of the cause of their thyroid disorder. This may require additional diagnostic testing but will help better-educate patients about the disease that is affecting them.

The copyright of the article Primary and Secondary Hypothyroid Disorders in General Medicine is owned by Jim Lowrance. Permission to republish Primary and Secondary Hypothyroid Disorders in print or online must be granted by the author in writing.