A patient diagnosed with hypothyroidism gets a routine lab test back showing high TSH (thyroid stimulating hormone) indicating her brain is signaling for more thyroid hormone.  Instead of increasing the dosage of her natural thyroid or investigating any secondary causes of the hypothyroidism, the prescribing physician puts our mutual patient on synthroid (synthetic thyroid).  Follow-up lab reports come back normal for TSH, the doctor thinks all is well, and our patient is in my office complaining of hair loss – one sign indicating continuing hypothyroidism.  This is all too common an occurrence.  What exactly is going on here?

Despite in-range lab values, I have witnessed many a patient not respond well to synthroid.  The drug does a great job of making the blood work appear normal but clinical signs and symptoms persist.  If the prescribing physician does not take this into account and simply relies on the labs, this patient will leave their office feeling that some other, now unaddressed, cause must be behind their continuing symptoms.  I have often asked these patients to return to their physician, or seek a second opinion, to evaluate whether a natural thyroid drug would be indicated.  Those who have, categorically respond better.  Why then the reluctance to use natural thyroid?

I could wax conspiratorial about drug reps pushing the sales of synthroid to dominate market share (and I wouldn’t be far from the truth) but the more practical reason cited is that synthroid is easier for doctors to regulate.  Because your body’s need for thyroid hormone changes from moment to moment, dosage and timing in taking natural thyroid requires more attention from patient and finesse from the physician.  If synthroid was as effective as natural thyroid, the story would end there, but this is often not the case as has been proven to me time and again.  The question then becomes why do patients persist with symptoms of hypothyroidism despite having in-range lab values?

My conclusion is that the standard serum indicators of hypothyroidism fail in two key ways.  The first is taking the overall number out of context of patient symptoms.  To fall within range for TSH, for example, is meaningless if the optimum level of thyroid hormone for that patient is produced when TSH is on the lower level of that range.  Being on the low end of normal on a thyroid panel and still having symptoms is a likely indicator of subclinical hypothyroidism.  The second reason why the standard panel fails to properly diagnose thyroid disorders is because of the existence but well understood cases of secondary hypothyroidism and thyroid hormone resistance.  

There are many types of secondary hypothyroidism, all sharing an inability for the body to express a healthy production or use of thyroid hormone.  They are termed secondary because the problem does not lie with the thyroid itself but with another organ or hormonal state that blunts the effect of thyroid hormone.  Traditionally, the term secondary hypothyroidism was reserved for a hypothyroid state deriving from an abnormality in the pituitary’s ability to signal the thyroid (and likewise tertiary hypothyroidism for an abnormality in the hypothalamus) but many practitioners have co-opted the term to help describe systemic hypothyroid states from other causes.

In a healthy individual the thyroid gland manufactures T4 which is then converted to T3, the active thyroid molecule.  T3 is then utilized by virtually every cell for a number of biochemical reactions.  Chronic stress and/or high blood sugar leads to an elevation of the adrenal hormone cortisol.  This causes T4 to be converted to reverse T3 in excess, an inactive form of T3 that blocks the receptors sites where the active T3 binds.  Thus, hypothyroid symptoms persist despite a perfectly functioning thyroid.


Another common cause of secondary hypothyroidism is an inability to make this conversion of T4 to T3.  Nearly 90% of the active thyroid hormone T3 gets it start via the gut, kidneys, and primarily the liver making the conversion from the T4 being actively circulated in the bloodstream.  Poor liver function will therefore leave you with a relative lack of active thyroid hormone, again a cause of persistent hypothyroid symptoms despite a healthy and functioning thyroid gland.

Yet another form of secondary hypothyroidism comes from a hormone state called estrogen dominance.  This condition of elevated estradiol relative to progesterone causes a low uptake of the active T3.  Here again, your thyroid is working fine but the fruits of its labor are being squandered due to a separate pathological state.

Coming back to the standard of care in allopathic medicine, the drug synthroid is poorly converted into the active form T3 in many individuals which accounts for the persistence of hypothyroid symptoms in the above patient.  This fact, combined with a normalized TSH in follow-up lab work, makes taking synthroid a pharmaceutical-created form of secondary hypothyroidism. 

In all cases, diagnosing and correcting the underlying reason for hypothyroid symptoms will get to the root of the problem.  An example of a comprehensive thyroid panel which can detect both primary and secondary causes includes the following tests: TSH, free T3, free T4, reverse T3, T3 uptake, TPO antibodies (to help diagnose autoimmune cases of hypothyroidism).

Finally, it is worth noting the common nutritional causes of poor thyroid function.  Abundant iodine, L-tyrosine, selenium, copper, and a healthy and happy gut flora (probiotics) are all needed for the full expression of your thyroid.  Avoiding soy foods, which suppress thyroid function, is also a must.  Any skilled holistic practitioner trained in endocrinology should be able to help you get to the underlying cause of your thyroid woes.  One thing is for sure, if you are experiencing symptoms of hypothyroidism, you are certainly NOT suffering from synthroid deficiency.  If you feel like your case has slipped through the medical cracks, it is your job to educate yourself and keep searching for proper treatment.  Your thyroid will thank you for finally being understood.  For more information, including all the relevant research with which to educate your doctor, visit the detailed website of the Holtorf Medical Group.  Leave your comments and questions below, and as always, thanks for reading.

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