TSH (Thyroid-Stimulating Hormone) Test: What does it mean?

TSH (Thyroid-Stimulating Hormone) Test: What does it mean?

Crystal's insightful blog for Mira delves into the critical topic of TSH, shedding light on its significance in thyroid function and its impact on fertility. Covering the basics, causes, and implications of both low and high TSH levels, Crystal emphasizes the importance of TSH testing for assessing thyroid and pituitary gland function. The article provides valuable insights for individuals seeking to understand and monitor thyroid disorders, emphasizing that TSH levels can influence fertility health. Crystal also explores the potential causes behind abnormal TSH results, offering a comprehensive guide for readers. Concluding with accessible testing options, including both clinical blood tests and convenient at-home finger-prick tests, the blog serves as an informative resource for those navigating thyroid-related concerns.Thanks, Mira, for this insightful piece! 

Written by Crystal for Mira

What is TSH?

TSH is a hormone made by the pituitary gland, a small structure found at the base of the brain. TSH controls your thyroid gland by telling it to produce two hormones known as T4 (thyroxine) and T3 (triiodothyronine). These hormones play a role in your body’s metabolism and can also affect your menstrual cycle and fertility indirectly. TRH, the hormone that regulates the production of TSH, can be influenced by cold temperatures and severe stress.

Why should you perform a TSH test?
  • To assess thyroid gland function
  • To evaluate pituitary gland function
  • To diagnose and monitor the treatment of thyroid disorders
  • To determine if thyroid function affects fertility health

What does it mean if my TSH results are low? 

If your TSH level is low, it means your thyroid hormones may be too high and needs to be lowered. This is known as hyperthyroidism—which can cause symptoms such as weight loss, rapid heart rate, nervousness, and difficulty getting pregnant.

Low result causes:

  1. Primary hyperthyroidism: When the thyroid becomes overactive, TSH levels may lower and thyroid hormone levels (like T4) may rise. This can happen due to conditions like Graves’ disease, thyroid nodules, or thyroid tumors.
  2. Damage to hypothalamus/pituitary gland: If there is damage to the hypothalamus     (a small region at the base of the brain that regulates important bodily functions and hormone release), or pituitary gland (a small gland at the base of the brain that produces and releases hormones, controlling various bodily functions), TSH levels may decrease, which can affect thyroid function.
  3. Excessive thyroid hormone medication: Taking too much thyroid hormone medication can cause the brain to reduce TSH production, leading to low TSH levels.
  4. Severe illness or chronic inflammation: When a person has a severe illness or chronic inflammation, their TSH and thyroid hormone levels may decrease due to non-thyroidal illness syndrome.
  5. Smoking: Smoking can contribute to low TSH levels.
  6. Certain medications/supplements: Certain medications or supplements, like glucocorticoids, dopamine, anti-seizure drugs, and biotin-containing supplements, can cause a false low TSH reading.

What does it mean if my TSH results are high?

High TSH levels usually mean your body needs more thyroid hormones. When TSH levels are high, it indicates that your thyroid hormone levels (T3 and T4) are low. This can happen when your thyroid gland doesn’t produce enough hormones, which is called hypothyroidism or an underactive thyroid gland. Hypothyroidism can cause symptoms like weight gain, fatigue, dry skin, constipation, feeling cold, irregular periods, and difficulties getting pregnant.

High result causes:

  1. Hypothyroidism or Hashimoto’s thyroiditis. A relatively common cause of hypothyroidism (underactive thyroid) is Hashimoto’s thyroiditis, an autoimmune disorder in which the immune system attacks and gradually destroys the thyroid gland.
  2. Iodine deficiency or excess iodine.
  3. Obesity and overeating. A study found that chronic overeating increased T3 levels over both the short- and long-term (from 3 weeks up to 7 months).
  4. Radiation therapy to the head and neck area.
  5. Toxins, drugs, and supplements. (e.g., lithium therapy, opioids, arsenic, dopamine inhibitors).
  6. TSH levels naturally increase as women age. 


Your hormonal level results are not a substitute for medical advice. Please consult with your healthcare provider.

How can I test TSH?

TSH is a blood test. You have two options to obtain results: 

  • Clinical blood test from a vein,
  • At-home finger-prick test, that is gaining popularity due to their convenience and privacy.