Root Causes of Suboptimal Thyroid Function

How could it be possible to experience thyroid-related problems even when routine labs show that thyroid function is “normal?” Let’s break this down. 

Here’s how your thyroid works:

A hormone called TRH is released from your hypothalamus (deep inside your brain), which triggers TSH release from your pituitary gland (also in your brain). TSH travels through your blood to trigger thyroid hormone production in your thyroid gland (at the base of your neck). 

Your thyroid gland produces 2 active forms of thyroid hormone that circulate through your body:

  • T4 (thyroxine)

  • T3 (triiodothyronine)

Even though your body makes much more T4 than T3, your T3 is about 4 times as powerful and considered an even more active form. Your body can also produce reverse T3 (rT3), which actually blocks thyroid function. 

The most common screening test for thyroid function is TSH. Even when that falls within the lab’s normal reference range, here are some possible scenarios to explain suboptimal thyroid function:

  • Insufficient production of T4

  • Insufficient conversion of T4 → T3

  • Increased production of reverse T3 (rT3)

That’s why—if you are struggling with unexplained exhaustion, brain fog, constipation, dry skin, hair loss, brittle nails, or any other signs of thyroid imbalance—it’s so important to have your doctor run a more comprehensive panel of thyroid tests. 

Of course, the next question to ask is what could be causing suboptimal thyroid function? Here are just a few of the possible root causes:

  • Exposure to environmental toxins (many chemicals disrupt thyroid function)

  • Autoimmunity (antithyroid antibodies can be detected in many people with suboptimal thyroid function)

  • Undereating or Overexercising (your thyroid controls your metabolism, so your lifestyle can throw it out of whack)

  • Stress (more to come on this!)

  • Nutrient insufficiencies (I’ll be talking about this in my next post!)

In functional medicine, we always aim to understand the root cause of your health concerns. We dig deep to look for patterns and explanations. And most importantly, we want to OPTIMIZE your health—because when you are not feeling your best, it affects every area of your life. 

Stick with me and watch for my next post—all about nutrients for thyroid health!