Which Lab Tests to Tackle the Thyroid Thicket?
(Part Two of Three, see Part One here.)
Here’s the million dollar question, because most large medical clinics have switched to “efficient” thyroid testing, which I would call perhaps efficient but in the long term, absolutely insufficient. Bare bones testing checks just the TSH (the messenger from the brain’s control center, turning on thyroid hormone production) with a “reflex to T4”, the free T4 only ordered if the TSH crosses a worrisome threshold, usually set too high, in my opinion. Such testing will identify “overt” hypothyroidism, namely when there is an elevated TSH and a sub-normal T4 level.
Current normals are usually set close to the following values for adults:
- TSH = 0.5-4.70 mIU/L
- Free T4 = 0.7-1.99 ng/dl (T4 accounts for the great majority of the hormone produced in the thyroid gland)
- Free T3 = 3.5-6.5 pmol/L (T3 is “activated” from T4 by the thyroid, liver, and various tissues in the body, and is the active, useful form of thyroid hormone)
Overt, clinical hypothyroidism occurs when the TSH is over 4.70, and levels of Free T4 and/or T3 are abnormally low.
On the other hand, subclinical hypothyroidism can also lead to other problematic health conditions – all of the conditions mentioned in Part I (see here) – and occurs when you have either an elevated TSH but the thyroid hormones themselves are normal or a so-called normal but not optimal TSH with normal or low thyroid hormones.
At least twice – 1995 in England, 2003 in the US – panels of experts agreed that the current upper limits of TSH were set too high, and missing genuine cases. The panels suggested lowering the acceptable levels of TSH to somewhere between 2 and 3.
But in the US in 2012, we went back to back to 4+ as the upper limit of normal. In my medical practice, I consider any TSH value over 2.0 as potentially problematic, and proceed according to the patient’s situation. If someone has numerous symptoms of hypothyroidism with a TSH over 2.0, I find that replacement is usually helpful, whether the T4 and T3 are normal or abnormal. With supplementation, the thyroid hormone levels usually stay about the same, but the TSH goes down to be low 2. It is the patient’s decision, based on symptoms or lab tests, whether to continue with thyroid in that situation.
But of course, in my own practice, I start with more than just the TSH. I consider a basic set of thyroid labs, ordered with any suspicion of thyroid imbalance, to include the following (with optimal results for each):
- TSH (0.3-2.0 ng/mL)
- Free T3 and Free T4 (in the upper half of lab’s reference range)
- Reverse T3 if there is any evidence of high stress levels (less than 5 X T3)
- Anti-thyroid antibodies, both TPO and Thyroglobulin (normal by lab range)
- Vitamin D (40-65 ng/mL)
- Ferritin (>60 ng/mL, or >80 if hair loss is a problem)
- Zinc (normal range)
- RBC Magnesium (normal range)
- Spot urine for iodine (>150 mcg/L)
- Homocysteine (< 8.0)
- Vitamin B12 and folate (upper half of the normal range)
You may think that a lot of vitamin, or nutrient, testing for a thyroid problem, and you are right. Thyroid hormone is very complicated to produce adequately, requiring adequate or optimal levels of the wide variety of nutrients listed above. Sometimes we find that apparently low thyroid numbers are associated with low iodine or low zinc levels. Normalizing those levels might make a prescription for thyroid hormone a temporary intervention, as opposed to the conventional medical “wisdom” that once you need thyroid hormone, you will always need it.
The antibody testing is not usually performed routinely, but I would argue that to be an illogical stance. It is estimated that 80-90% of all disorders of thyroid hormone production (and some disorders of thyroid nodule formation) are auto-immune in nature. In many if not most cases of autoimmune thyroid disease, gluten is a powerful culprit. Gluten causes at least transient leaky gut (increase in intestinal permeability) in all people, and persistent leaky gut is thought to be a significant component of autoimmune disease in general, and thyroid disease in particular, as the gluten molecule bears an uncanny resemblance to normal thyroid tissue.
You can see why I consider Thyroid Disease to be a largely Neolithic condition. Whether it is nutrient deficiencies or exposure to gluten, these are both conditions more associated with our modern, agricultural diet and lifestyle, and not present during Paleolithic times. I encourage patients with autoimmune disease to take the Paleo challenge: six weeks without grains, legumes, or dairy. Symptom relief can be dramatic. Re-introduction of foods proceeds one food at a time (three days per food), and I suggest gluten is permanently on the "rare occasions only" list.
Additional testing that I consider:
- Cyrex Labs gluten sensitivity testing in a patient with positive antibodies is reluctant to go off of gluten.
- NutrEval from Genova Diagnostics when preliminary testing identifies nutritional deficiencies.
- GI Effects from Genova Diagnostics for malabsorption if the diet is adequate but nutrient levels are low.
- ASI (Adrenal Stress Index) from DiagnosTechs if any sleep disturbance.
Then there is the topic of thyroid replacement, which is also complicated, and I’ll get to in Part Three.