TSH (stands for stimulating thyroid hormone) is part of the feedback loop to control the levels of thyroid hormone. TSH levels are high when some parts of this feedback loop are not working properly. The most common cause is a problem in the thyroid, causing hypothyroidism, and treated with the same hormone. A tumor in the pituitary or hypothalamus can also cause high levels of TSH and hyperthyroidism. A CAT scan and thyroid tests may help identify the cause.
Feedback loop TSH
TSH is a protein hormone released by the pituitary gland in the brain that stimulates the thyroid to produce thyroid hormone, which regulates body metabolism. TSH is released from the pituitary gland in response to the release of TRH (stands for thyroid hormone release) from the hypothalamus (also in the brain). A negative feedback circuit, thyroid hormone sends a signal to the hypothalamus regularatoria to decrease levels of TRH.
Hyperthyroidism and hypothyroidism
When TSH levels are high, two opposite conditions may occur: the body produces too much thyroid hormone (hyperthyroidism) or not make enough (hypothyroidism). Hyperthyroidism is a condition in which metabolism is accelerated. A person can lose weight, have rapid heartbeat, sweating excessively, be intolerant to heat, become anxious, have difficulty concentrating, and have osteoporosis and diarrhea. Hypothyroidism is the opposite condition, a slower metabolism with weight gain, slow heart rate, cold skin, intolerance to cold, poor growth and constipation.
If the thyroid gland can not produce thyroid hormone, the body anyway to continue sending signals to occur, as a collector who keeps asking for money. That signal is the TSH and the most common cause of high TSH is hypothyroidism. The thyroid may be unable to produce thyroid hormone if there is not enough iodine in the diet (cretinism); If the thyroid is under immune attack (Hashimoto's disease); It has been surgically removed; It has become fibrous (Riedel's thyroiditis) or it is inflamed by a viral infection (Quervian thyroiditis). There is a small risk of thyroid cancer with high levels of TSH.
Pituitary and hypothalamus
Pituitary and hypothalamus are parts of the brain. A rare pituitary tumor (pituitary adenoma) may create too much TSH. Still less common tumor formed in the hypothalamus may release TRH, TSH levels causing increase.
Diagnosis of hypothyroidism
The problem can be identified if the level of thyroid hormone and iodine are measured. Low levels of thyroid hormone suggest that the thyroid is not functioning normally. Iodine levels should also be inspected. Thyroid scan determines if it is working. Fortunately, thyroid hormone can be replaced, correcting levels of TSH.
Diagnosis of hyperthyroidism
If a tumor in the pituitary gland, which is rare, HRT levels will be low because high levels of thyroid hormone will tell the hypothalamus to stop producing HRT. If there is a tumor in the hypothalamus (very rare), then the levels of TRH and thyroid hormone will be high. However, practically, the combination of a CT scan or an MRI and a substitute thyroid hormone T3 identify these foreign tumors as HRT can not be measured.