Thyroid Stimulating Hormone
Otherwise known as thyrotropin, the thyroid stimulating hormone (TSH) is released from the anterior pituitary gland. As its name suggests, the main function of this hormone is to stimulate the thyroid gland to either synthesize or secrete T3 and T4 into the body. It controls the rate of thyroid hormone release.
This hormone plays a significant role in regulating cellular metabolic activity. Once released, a cascade of mechanisms triggers the release of specific enzymes that contribute to both oxygen consumption and tissue responsiveness. The thyroid-stimulating hormone, together with other thyroid hormones, is necessary for cell replication and largely contributes to optimal brain development. This interplay influences every major organ system.
Thyroid Stimulating Hormone Levels
Thyroid stimulating hormone levels primarily depend on the concentration of thyroid hormones in the blood. Secretion of TSH depends on the negative-feedback system. For example, a decrease in thyroid hormone results to the increased release of thyroid stimulating hormone. An elevated T4 level suppresses TSH release and secretion.
A patient may undergo blood tests to determine hormone blood levels. The single best diagnostic test for thyroid function is the measurement of serum thyroid-stimulating hormone concentration. Once suspicion of a thyroid disorder is established, serum levels of thyroid-stimulating hormone can provide doctors information about the nature and site of the disease.
TSH and T4 levels are frequently measured to differentiate thyroid dysfunctions.
- Measurement of this hormone can be used to monitor ongoing replacement therapies.
- Levels can distinguish whether the disease is a problem of the thyroid, pituitary, or hypothalamus.
- TSH levels are measured to suggest secondary hypothyroidism due to pituitary involvement.
Thyroid Stimulating Hormone Test Results
Results can indicate hypofunction or hyperfunction of the organ, or point out the malfunctioning organ, which includes the thyroid gland, the pituitary, or the hypothalamus. A small deviation from the normal levels can distinguish subclinical thyroid disease from normal thyroid states. The normal range of TSH levels range from 0.4 to 6.15 micro units per mL.
- A value above the normal range indicates primary hypothyroidism, thyroiditis, cirrhosis of the liver, and antithyroid therapy.
- Those below this range indicate secondary hypothyroidism, anterior pituitary hypofunction, Klinefelter’s syndrome, or drug influence.
- A decreased T4 level and a normal or elevated TSH level indicates a thyroid disorder.
- A decreased T4 level with a decreased TSH level can indicate a pituitary disorder.
To achieve accurate test results, consumption of shellfish should be avoided for several days before the test. No fluid restrictions are necessary.