What is thyroid-stimulating hormone?
Thyroid-stimulating hormone (TSH) is a hormone produced by your pituitary gland. TSH stimulates your thyroid to produce the thyroid hormones triiodothyronine (T3) and thyroxine (T4).
What is its function?
TSH helps regulate the production of T3 and T4 (thyroid hormones). These hormones play a key role in regulating your metabolism — for example, they help regulate your heart rate, body temperature, and breathing.
If your T3 and T4 levels are low, more TSH is produced. This stimulates your thyroid to produce more T3 and T4. If your T3 and T4 levels are high, less TSH is produced.
What can cause it to change?
If your thyroid is overactive (hyperthyroidism) it can cause low TSH levels — due to high T3 and T4 levels.
If you're taking any medication containing T3, it might affect your results. To avoid this, it's best to take your blood sample first thing in the morning after fasting.
If your thyroid is underactive (hypothyroidism) it can cause high TSH levels — due to low T3 and T4 levels.
If you're over or under-treating an existing thyroid condition with medication, your TSH levels could be out of range. Other causes might include:
- chronic illness
- an acute severe illness
- some medications
- a problem with your pituitary gland
What are the most common symptoms?
If your thyroid is overactive (causing low TSH), common symptoms include:
- weight loss
- increased appetite
- excessive sweating
- sensitivity to heat
- irritability and anxiety
- heart palpitations
- difficulty sleeping
If your thyroid is underactive (causing high TSH), common symptoms include:
- weight gain
- dry skin
- brittle hair
- sensitivity to cold
- memory problems
- muscle aches
- hoarse voice
In women, high or low thyroid hormones might affect your period — for example, it might cause heavy or irregular periods.
What can I do to change my levels?
There are a number of nutrients that are important for your thyroid function:
- Iodine — helps make thyroid hormones
- Zinc — helps make thyroid hormones
- Selenium — helps make thyroid hormones
- Iron — plays an important role in thyroid hormone metabolism
- Vitamin D — plays an important role in your immune function and low levels are linked to autoimmune thyroid disorders
If your levels indicate you have a thyroid disorder, it’s important to work with your doctor to come up with a treatment plan.