…Production of TSH follows a circadian rhythm that is it follows a 24-hour cycle with regular fluctuations. TSH production peaks at its highest level between 2:00 and 4:00 am each morning and then drops reaching its low point between 4 and 8 pm in the evening. Though this phenomenon is well known the actual extent of these fluctuations was much greater than was previously thought.
In this current study, researchers from the Federal Endocrinological Research Centre in Moscow, tested 20 women with subclinical hypothyroidism. Morning and afternoon TSH levels were measured and compared. The median morning TSH value for women with subclinical hypothyroidism was 5.83 mU/L. Their afternoon median TSH dropped down to 3.79 mU/L. Following the current guidelines for diagnosis hypothyroidism would have been diagnosed in only half of these cases when tested in the afternoon.
These new data explain why many people who appear to have symptoms of hypothyroidism have been told their test results were normal, that they are fine, when in truth they hypothyroid. TSH levels measured in blood samples drawn in the afternoon should be viewed with caution, as they may be falsely low and appear normal. Samples for all thyroid tests should be collected first thing in the morning.
It gets more complicated than this. Many practitioners consider the current normal range for TSH values to be too broad. Rather than judging TSH levels above 5 as hypothryoidism, some consider the upper limit of normal to be as low as 3.0, while researchers looking at what is called sub-clinical hypothyroidism define the condition by a TSH greater than 2.5. Apparently that is the level at which risk for cardiovascular disease increases significantly.
Good diet, sufficient calories, low stress (i.e. low cortisol, which interferes with conversion), adequate zinc and selenium and l-tyrosine all help in T4-T3 conversion. If you are taking T4 and still do not feel that good, one or more of these factors may be less than optimal. For me, adding l-tyrosine about one hour after a light breakfast has helped. ABN
American Buddhist Net 