Learn what high TSH and normal T4 levels say about thyroid health and what you can do about them.
The two thyroid hormones, T3 and T4, are released by thyroid gland in the throat. TSH is released by the pituitary gland located in the lower back of our brain (which is called hypothalamus).
TSH is called thyroid stimulating hormone because through it, the pituitary tells (stimulates) the thyroid to release these two thyroid hormones. Therefore, TSH works as a nob that maintains optimal T3, T4 levels with the increase or decrease of TSH in the blood.
For example, whenever T4 levels drop, pituitary raises TSH levels which tell (stimulate) the thyroid to release more T4. If T4 is too high, TSH levels drop to reduce them. Therefore, thyroid stimulating hormone (TSH) and T4 work together to maintain our health.
Any problems with the thyroid gland first show up as unusual reading of TSH levels. That's because whenever the gland can't make enough T4 and T3, a change in TSH levels will try to compensate for it. Only after this compensation fails, T4 levels will become abnormal. This is also the reason why TSH levels are the first thing to check when in doubt.
Depending on your symptoms, there are a few possible combinations that might show up in your report. Here we go through all these possible combinations.
This is an early sign of an underactive thyroid that can't make sufficient T4. At first, the pituitary releases extra TSH to drive it harder and normalize T4 levels in the blood.
This early stage is called subclinical hypothyroidism and you may not see any symptoms yet. If thyroid can no longer produce enough T4, then TSH levels will keep rising. Soon you may start to gain weight, feel unusually cold and lethargic with a loss of appetite.
They indicate more than usual activity in thyroid gland. As a result, pituitary tries to slow down the thyroid and maintain optimal T4 by reducing TSH until the later drops to almost zero. This early stage is called subclinical hyperthyroidism. It's subclinical because the full fledged symptoms, that a doctor or clinician can notice, haven't appeared yet. But soon you may start to feel agitated, anxious, unusually sensitive to heat with uncontrollable appetite, and may even lose some weight.
Once pituitary can't compensate for the slow thyroid, T3 and T4 levels fall. This causes persistently high TSH and low T4, T3 levels. The symptoms also become clear and a blood test can be used to confirm.
Once TSH levels hit the floor and can't go any lower, the T4, T3 levels will start increasing. This leads to clear symptoms of hyperthyroidism and a blood test will show near zero TSH and extremely high T4 values.
High levels of both TSH & T4 (or low levels of both) are extremely rare and indicate problems with the pituitary gland. Since TSH and T4 compensate for each other, unusually high or low levels of both are due to additional problems, such as a tumor, autoimmune disease or other unknown reasons.
Because TSH and T4 work so well together, it is important to check both of them in a lab test. Even if TSH levels are normal, it is possible they are compensating for a slow or fast thyroid gland which can't be confirmed with a TSH test alone. Also, T4 and T3 continuously change into each other, it's also important to know the optimal levels for both of them.
A simple finger prick test from RxHomeTest can measure all three markers. The sample is stable for 30 days at room temperature & can be easily collected and mailed to a CLIA-certified lab. If you want to get more info, a test with TPO antibodies and reverse T3, is also available.
Order an At-Home Thyroid Test.
All About Thyroid - an in depth summary.
Normal TSH Levels: What's Normal and Why? - a detailed look at thyroid stimulation hormone.
Five Common Thyroid Problems To Watch Out For - a review of most common problems.
The Difference Between Hypothyroidism and Hyperthyroidism - a quick look at key differences.
Thyroid and Pregnancy - about the critical role thyroid plays during pregnancy.
Thyroid and Iodine - thyroid problems depend on lack or excess of iodine.
