Tsh normal range

Thyroid disease is common in the general population, and its prevalence increases with age. Because the signs and symptoms of the disease often resemble other disorders, before initiating treatment physicians need to determine whether the patient actually has thyroid disease or something else. The test most frequently ordered to test thyroid function is thyrotropin, commonly referred to as thyroid-stimulating hormone (TSH). Based on the functional interrelationship of the hypothalamus, pituitary gland, and thyroid, TSH should be elevated if the thyroid gland is not producing adequate thyroid hormone, and suppressed if it is producing too much (Figure 1). Today, however, we are beginning to realize that this well-established paradigm for TSH synthesis and release is an oversimplification. Figure 1 Thyroid Functions The hypothalamus releases thyrotropin releasing hormone (TrH), which travels via a venous plexus to the anterior lobe of the pituitary gland and stimulates release of thyroid stimulating hormone (TSH). TSH then induces production of thyroxine (T4) by the thyroid. In response to the concentration of free T4, which influences the amount of triiodothyronine (T3) produced in each site, both the hypothalamus and the pituitary alter production of TrH and TSH, respectively. Elevated free T4 inhibits production, while low free T4 stimulates production. Not only does the pituitary secrete TSH in a diurnal pattern, but many substances produced in the central nervous system...