What Does a Low TSH Mean

Thyroid stimulating hormone or TSH is one of the crucial hormones in the body that plays an important role in various metabolic functions, by regulating the function of the thyroid gland. TSH is released by the anterior pituitary gland to stimulate the thyroid gland. Thyroid releases the hormones T3 and T4 which regulate the body metabolism. Whatever iodine you consume is converted into hormones by the thyroid gland.

As normal TSH level range for reference varies from lab to lab, it creates ambiguity in the minds of common people. Originally, the range 0.5 to 5.5 mIU/L (milli-international units per liter) of TSH was considered as normal. But according to the revised American standards, TSH range 0.3 to 3.3 mIU/L is considered as normal.

However, some labs still follow the old normal TSH levels range for reference while some follow 0.4 - 4.0 mIU/L as normal TSH range.

Considering the revised scale, TSH lower than 0.3 mIU/L suggests hyperthyroidism and TSH level greater than 3.0 mIU/L indicates hypothyroidism (an under-active thyroid); as the pituitary gland starts releasing more TSH to stimulate the under-active thyroid.

Hyperthyroidism

If the thyroid starts releasing more T3 and T4, the condition is known as hyperthyroidism. To control the over-activity of the thyroid gland, pituitary gland restricts the flow of TSH as there is no need to stimulate the thyroid. So TSH levels drop during hyperthyroidism.

Non-Functioning Pituitary Gland

Dysfunction of pituitary gland can affect the production of TSH. This condition is very rare. Healthy diet and regular exercise are essential to maintain the functions of the glands in the body.

Along with TSH, thyroid hormone levels are also measured. If both T4 and TSH levels are low, it suggests that pituitary gland is not working properly. This would result in hypothyroidism.

Doctors advise to increase the intake of foods rich in iodine and selenium as these foods work great for hypothyroidism. Since the pituitary gland regulates the function of adrenal glands, ovaries and testicles, other symptoms would also be noticed which would confirm pituitary dysfunction.

The pituitary gland plays an important role in growth of children and kidney function. So, hampered growth of children or kidney dysfunction indicates pituitary dysfunction.

Regular practice of yoga, meditation and breathing exercises like Pranayama help enhance the function of the pituitary gland. It is believed that correct and repeated pronunciation of 'AUM' before starting yoga or meditation helps stimulate the pituitary gland. A tumor of the pituitary can lead to low TSH levels.

Hypothalamus Dysfunction

Another rare condition, hypothalamus dysfunction can result in diminished TSH levels. A trauma or injury, a tumor in brain can result in hypothalamus dysfunction. The hypothalamus releases two antagonistic hormones 'thyrotropin' and 'somatostatin' which help regulate pituitary activities.

Imbalance of these hormones can affect pituitary function and the TSH levels.

Medications

Excessive consumption of thyroid hormone replacement drug can lower TSH levels. At times, to control an overactive thyroid, doctors prescribe some medications which lead to excessively low TSH levels. The dose has to be adjusted taking into consideration the effects of the medications.

Diminished TSH levels are normally observed when the thyroid becomes overactive. Symptoms of hyperthyroidism include:

• Heat intolerance
• Excessive sweating leading to weakness
• Impotence in men

• Increased rate of metabolism
• Increased bowel movements owing to the increased rate of metabolism
• Rapid heart rate, palpitations
• Agitation, nervousness and tremor
• Increased anger, irritability
• Severe mood swings, sudden attacks of nervousness

• Increased appetite
• Weight loss despite increased appetite
• Decreased concentration
• Low energy levels, fatigue

• Hot flashes, joint pain in women
• Insomnia, difficulty sleeping
• Light and less frequent menstrual periods or absence of menstruation
• Osteoporosis, low bone density
• Rapid peristalsis, fast movement of the muscles of the alimentary canal, resulting in fast movement of the ingested food

Following a 'thyroid diet' designed by the doctor, taking medicines and exercising, help improve TSH levels. You should check your routine medications as well. Consult with your doctor to confirm that none of your routine medications are causing low TSH levels. Fluctuations in blood sugar levels can affect the functions of the glands in the body. Leading a stress free lifestyle helps maintain normal hormone levels.