Thyroid-Stimulating Hormone (TSH)

Metabolic Health

TSH stands for thyroid stimulating hormone, though it is sometimes called thyrotropin or thyrotropic hormone. TSH stimulates the thyroid gland to produce thyroid hormone, which is is critical for the proper function of virtually every cell in the body. TSH is released by the pituitary gland after the gland has been stimulated by thyroid releasing hormone (TRH), which is secreted by the hypothalamus. Thyroid hormone provides negative feedback on the hypothalamus and/or the pituitary to reduce thyroid hormone production and release. TSH measurements are important for diagnosing hypothyroidism and hyperthyroidism. TSH may be measured in conjunction with total thyroxine (T4), total triiodothyronine (T3), free T4, free T3, and reverse T3 concentrations in the serum.

Normal Ranges for TSH:

  • Children
    •   1-2 Days 3.20-34.60 mIU/L
    •   3-4 Days 0.70-15.40 mIU/L
    •   5 Days-4 Weeks 1.70-9.10 mIU/L
    •   1-11 Months 0.80-8.20 mIU/L
    •   1-19 Years 0.50-4.30 mIU/L
  • Adult (non-pregnant) 0.40-4.50 mIU/L
  • Pregnancy  
    •   First Trimester 0.26-2.66 mIU/L
    •   Second Trimester 0.55-2.73 mIU/L
    •   Third Trimester 0.43-2.91 mIU/L

 

Sources:

http://www.uptodate.com/contents/thyroid-hormone-synthesis-and-physiology

http://www.ncbi.nlm.nih.gov/pubmed/2194786

http://www.uptodate.com/contents/laboratory-assessment-of-thyroid-function

http://www.questdiagnostics.com/testcenter/TestDetail.action?ntc=899

http://www.uptodate.com/contents/disorders-that-cause-hypothyroidism

http://www.uptodate.com/contents/disorders-that-cause-hyperthyroidism

http://www.ncbi.nlm.nih.gov/pubmed/21048053

http://www.nejm.org/doi/full/10.1056/NEJMcp0801880

http://www.uptodate.com/contents/disorders-that-cause-hyperthyroidism

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The healthy result should fall into this range:

0.5 - 4.5 mIU/L

0.50 - 4.50 IU/L

Learn more how Thyroid-Stimulating Hormone (TSH) can effect your health

If your result is too high.

High TSH levels are usually caused by primary hypothyroidism or subclinical hypothyroidism. When thyroid levels are low, the hypothalamus and pituitary gland try to increase thyroid hormone production by raising TSH levels. Hypothyroidism may cause weakness and fatigue, cold intolerance, shortness of breath, weight gain, constipation, cognitive problems, dry skin, hoarseness, and swelling (edema).

Some specific causes of high TSH are:

  • Transient hypothyroidism 
  • Painless thyroiditis  
  • Subacute granulomatous thyroiditis  
  • Postpartum thyroiditis  
  • Subtotal thyroidectomy  
  • Radioiodine therapy
  • Chronic autoimmune thyroiditis 
  • Thyroidectomy 
  • Iodine deficiency or excess 
  • Fibrous thyroiditis
  • Sarcoidosis 
  • Hemochromatosis
  • Congenital thyroid agenesis, dysgenesis, or defects in hormone synthesis
  • Generalized thyroid hormone resistance
  • Drugs such as lithium or amiodarone

If your result is too low.

High TSH levels are usually caused by primary hyperthyroidism or subclinical hyperthyroidism. When thyroid levels are high, the hypothalamus and pituitary gland try to decrease thyroid hormone production by lowering TSH levels. Graves' disease is the most common cause of hyperthyroidism, though the other major autoimmune thyroid disease, Hashimoto thyrotoxicosis (i.e. Hashitoxicosis), is also quite common. Hyperthyroidism may cause excessive appetite, anxiety, heart palpitations, sweating, shortness of breath, weight loss, and intolerance to heat.

Some specific causes of low TSH are:

  • Graves' disease
  • Thyroiditis (e.g. postpartum thyroiditis, de Quervain's thyroiditis)
  • Euthyroid sick syndrome
  • Excessive thyroid hormone replacement therapy
  • Iodine-induced hyperthyroidism 
  • Toxic nodular goiter
  • Amiodarone

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