Research Update CHF 02686-A MY3: Pattern of Thyroid Function Tests during Recovery from Acute Nonthyroidal Illness

To date, 93 cases have been screened for possible study enrollment. Of these, 23 have fulfilled all of the enrollment criteria (92% of total cases needed) and are still in the study, 7 were enrolled but ultimately excluded (either determined to have a chronic disease, did not follow-up, or determined to have overt or subclinical hypothyroidism), 8 were not enrolled despite having a low total T4 (owner did not allow for study enrollment or found to have a chronic disease during diagnostic work-up), and 55 had a normal total T4 (failed to fulfill this inclusion criteria).

Based on the case enrollment thus far, 19/21 dogs had normalization of total T4 by the 2-week recheck. Thus, in dogs where acute nonthyroidal illness is diagnosed, rechecking the total T4 two weeks after nonthyroidal illness resolution will result in an accurate assessment of thyroid hormone status for most patients. For those not normal at 2-weeks, a recheck again 2-weeks later (at the 4-week mark) would be most appropriate, as all dogs had a normal total T4 by 4 weeks.

As expected, 100% of dogs at that time of nonthyroidal illness diagnosed had a low total T4 and ~90% had a low total T3. These values returned to normal as the disease process resolved. Free T4 (low) and TSH (high) was normal in all but 8 cases. The TSH, in most cases, appeared to significantly increase at the 2- and/or 4-week rechecks, albeit still within the reference range. Interestingly, in three cases, the TSH increases above the reference range after normalization of all other thyroid hormones (total T4, free T4, total T3) prior to returning to normal.

Enunciating differences between the pattern of thyroid hormone recovery in dogs and humans with naturally occurring disease will be postponed until all cases are enrolled and analyzed

Mid-Year 3 Update – Pattern of Thyroid Function Tests during Recovery from Acute Nonthyroidal Illness