All day long I have people come in to my office with every thyroid symptom in the book, but their MD ran a lab and said it was “normal.” This lab that they are referring to is TSH (Thyroid Stimulating Hormone). This number is nothing but an assumption about what a person’s hormone levels are downstream. TSH stimulates the thyroid gland to produce T4. T4 then feeds back to the pituitary gland dictating how much TSH is produced. It is a feedback loop and the assumptions are simple. ?TSH= ?T4 and ?TSH = ?T4. The problem is a few things…
- T4 is inactive in the body. It needs to be converted to T3 to have an effect. Many people lack conversion factors and are not actually converting to any active hormones. Every cell in your body has a receptor for T3 (active thyroid hormone). This is why the symptoms of low thyroid function can be so varied. You may have plenty of T4 and a normal TSH, but if you aren’t converting to T3 then you still have all the thyroid symptoms.
- A major site of this conversion is in the liver. In the state of today’s society most people have problems with liver congestion. This equates to decreased thyroid conversion and decreased thyroid function… even though your TSH is normal!
- Most importantly, the feedback loop from T4 to TSH is inhibited by cortisol, a stress hormone. So if you are under stress, and who isn’t? The feedback loop determining your level of TSH is broken. Rendering the value of TSH useless in detecting low thyroid hormone.
This is all only a snippet of the things that could be affecting thyroid function. The moral of the story is, when your doctor only tests TSH and sends you on your way with fatigue, constipation, weight gain, hair loss, poor memory, depression and other thyroid related symptoms, telling you that your labs are normal. They are doing you a huge disservice. They are only making assumptions about your hormone levels based on a frequently flawed feedback loop. Appropriate testing must be performed to make that call.