Do normal lab results always mean optimal thyroid function?
The short answer is: not necessarily.
To start, it’s important to understand how the thyroid functions. The thyroid is part of the endocrine system, which is made up of glands that produce and secrete hormones that regulate many of the body’s functions.
The hypothalamus is a portion of the brain that links the nervous system to the endocrine system via the pituitary gland. The pituitary gland (commonly referred to as the “master gland”) controls the function of numerous other targeted endocrine glands, including the thyroid which produces thyroid hormone.
Enter the thyroid-hypothalamus feedback loop
The thyroid gland receives input from the hypothalamus via the pituitary gland and, in return, provides positive and negative feedback to regulate normal function.
The hypothalamus produces thyrotropin-releasing hormone (TRH) and sends it to the pituitary. Once received, the pituitary produces thyroid-stimulating hormone (TSH) and sends it to the thyroid. Then, the thyroid’s job is to make and store hormones - most notably, T3 and T4 - that regulate the body’s metabolism in the form of blood pressure, blood temperature, and heart rate.
When low levels of thyroid hormone are sensed by the hypothalamus, it increases its release of TRH, causing the pituitary gland to increase its release of TSH. The increased levels of TSH will result in an increased production of thyroid hormones, returning the body to normal function. This is known as a positive feedback mechanism.
Alternatively, if thyroid levels become too high, the hypothalamus will stop sending TRH to the pituitary. Then, the pituitary will stop sending TSH to the thyroid, and the thyroid will stop the production and release of thyroid hormone until proper thyroid function levels are reached. This is known as a negative feedback mechanism.
Typically, the body does a great job at regulating itself to keep us at “normal” levels, but what happens when there is a disorder affecting one of these glands mentioned above and no matter how hard the body tries to counter regulate it, it just can’t keep up?
Markers used to test thyroid function
Traditionally, many doctors only test for Thyroid Stimulating Hormone (TSH) to assess thyroid health. TSH is the most sensitive marker for assessing both hypothyroidism and hyperthyroidism, but it doesn’t give a complete picture of what’s happening with the thyroid. TSH is a hormone produced in the pituitary gland in the brain. It regulates the amount of Thyroxine (T4) and Triiodothyronine (T3) produced by the thyroid gland.
- If TSH is high, it may be a sign that the body is under producing thyroid hormones. This may be indicative of hypothyroidism.
- If TSH is low, it may be a sign that the body is over producing thyroid hormones. This may be indicative of hyperthyroidism, or that your supplemental thyroid hormone dose is too high.
- If TSH is normal, it may indicate that there is no thyroid dysfunction.
However, the question we're trying to answer is, do “normal” lab results always mean optimal thyroid function? Even if your lab results report normal TSH levels, you may still have symptoms indicative of thyroid dysfunction. You need to a full thyroid blood panel to get the big picture.
Thyroxine (T4) is the main hormone that is produced and secreted by the thyroid gland. Without enough T4 (and its counterpart T3), the body’s metabolism slows down. T4 and T3 are in charge of your body’s energy usage. T4 is mostly inactive (called a storage hormone); its primary function is to transport T3 to the proper organs in your body.
- If fT4 is high, it can indicate an overactive thyroid or hyperthyroidism.
- If fT4 is low, it can indicate underactive thyroid or hypothyroidism.
Triiodothyronine is the active thyroid hormone that works at the cellular level to help with the delivery of oxygen and energy to cells, tissues, and glands throughout the body. The body must convert T4 into T3 to be used by cells. Without enough T3, the metabolism slows down.
- If fT3 is high, it may indicate that your thyroid is overactive or hyperthyroid.
- If fT3 is low, it may indicate that the body is not effectively converting T4 to fT3. You may have hypothyroid symptoms even if your TSH and fT4 are in the “normal” range.
The most common cause of hypothyroidism in the United States is Hashimoto’s Thyroiditis, an autoimmune disorder that damages the thyroid gland. Antibodies directed against the thyroid gland lead to chronic inflammation, decreasing its ability to produce thyroid hormone.
- If antibodies are elevated, it suggests that your immune system is attacking your thyroid, indicating autoimmune thyroid disease.
Traditionally, doctors rarely test for thyroid antibodies. At Paloma Health, we believe it’s critical to measure Free Triiodothyronine (fT3), Free Thyroxine (fT4), and TPO antibodies.
Normal versus optimal ranges
Normal thyroid function level is a reference range that is based on the average values in a population, rather than individualized values. This reference range does not take into account the clinical picture of the patient but is simply the average values and standard deviations of adults in an area.
Patients whose lab values fit within these “normal” ranges, but who still experience hypothyroid symptoms, are often dismissed or mistreated with a one-size-fits-all approach. This fails to address the root cause of thyroid dysfunction.
Optimal thyroid function is the level at which a person falls within the normal range, while simultaneously showing no signs or symptoms. Of course, this varies person-to-person.
Proper assessment and treatments
So, what to do if you if your “normal” lab results don’t equate to optimal thyroid function?
- Find a Care Team who you trust.
- Ask your doctor for a complete thyroid panel, or take matters into your own hands with our at-home thyroid test kit.
- Work with your doctor to consider all treatment options based on your symptoms, history, and lab results.
- Consider your lifestyle, diet & nutrition, movement, stress-management.
It’s time to get your thyroid back to optimal function! You can schedule a free call with a Paloma Health Care Advisor to determine if Paloma Health is the right fit for you.