Why do I feel so bad when my TSH is normal?
How many of us have heard a story from a friend (or ourselves) who has normal labs but feels absolutely terrible and just isn’t getting by in her day to day life. This is a super common experience and many of my patients describe feeling disbelief at the site of normal TSH on their lab results. A TSH level is 1/3 of the story when it comes to thyroid health. This is precisely why it’s important that your doctor checks a TSH along with other thyroid hormones, and thyroid specific antibodies.
To understand your thyroid, we have to first understand how it communicates with the brain. The brain acts like the CEO of the thyroid gland, controlling what and how much thyroid hormone the thyroid gland makes. The brain does this by sending down a signal to the thyroid gland called TSH. TSH stands for Thyroid Stimulating Hormone.
Just like the name sounds, TSH stimulates the thyroid gland, essentially turning on the “machines” that make 2 types of thyroid hormones, T4 and T3. Your brain and thyroid gland are in a constant conversation.
The brain “talks” to the thyroid gland using TSH, and the thyroid gland “talks back” to the brain using T4 and T3.
If the brain is happy with the amount of T4 and T3, the TSH stays put. If the brain is unhappy with the level of T4 and T3, the amount of TSH changes. With hypothyroidism, the thyroid gland can’t make enough T4 and T3. (T4 and T3 values get flagged for being low on lab results). In response, the brain sends out a stronger signal of TSH. (TSH gets flagged for being high on lab results).
A normal TSH on lab work is telling us that the brain is doing its job and functioning, but it doesn’t reveal what has gone wrong in the thyroid gland.
When we just check a TSH level on bloodwork, and it comes back normal. This normal TSH is telling us that the brain is doing its job, but it doesn’t tell us exactly has gone wrong in the thyroid gland. This is why it’s imperative that T4 and T3 actually get looked at along the way. From ignoring the brain’s TSH signal to being attacked by immune cells, there is a lot that can go wrong in the thyroid gland itself.
Autoimmune conditions of the thyroid gland, like Hashimoto’s, can exist even when TSH, T4, and T3 are normal on labs.
The thyroid can keep up with T4 and T3 production quite well, for a very, very long time while all along it is being slowly destroyed by your immune system. In fact, your body can do such a great job and trying to counteract this attack that the labs are normal even if the thyroid isn’t functioning at peak performance. 
Because of the resiliency of the thyroid gland, Hashimoto’s often goes undiagnosed for years. Then eventually, when enough damage is done, you can have an obviously low thyroid on labs and the debilitating symptoms to match. Recent studies are showing that the presence of thyroid antibodies alone, with normal thyroid function lab tests can be associated with symptoms that we commonly associate with Hashimoto’s like depression, fatigue, and brain fog. [1, 2] This suggests that antibodies may be significant contributors if not the cause of some of the classic Hashimoto’s symptoms.
If you want to get to the bottom of your thyroid troubles and finally see the complete story, it’s going to take more than just a TSH.