1/2. Elevated thyroxine and free thyroxine in euthyroid patients: familial dysalbuminemic hyperthyroxinemia.An eleven year old male was evaluated because of persistent elevation of thyroxine levels and elevated thyroxine index calculated as "T7" but normal thyrotropin levels. The findings were demonstrated by thyroxine binding protein electrophoresis to be due to aberrant thyroxine binding to albumin. The abnormality was also documented in the patient's father. This entity, known as familial dysalbuminemic hyperthyroxinemia, is being reported with increasing frequency and should be suspected when elevated total thyroxine and free thyroxine or "T7" levels are associated with a normal thyrotropin level. The case reported is somewhat unusual in that the triiodothyronine affinity of the aberrant protein appears to be more pronounced than usually reported with this syndrome and the corresponding total triiodothyronine level was significantly elevated.- - - - - - - - - - ranking = 1keywords = index (Clic here for more details about this article) |
2/2. Reverse T3 does not reliably differentiate hypothyroid sick syndrome from euthyroid sick syndrome.To assess the efficacy of reverse T3 in differentiating between the hypothyroid and euthyroid state in the setting of illness, all reverse T3 determinations obtained over a 4-year period in a University teaching hospital were analyzed in the context of concurrent thyroid function tests, bilirubin, albumin, creatinine, subsequent treatment, and follow-up. Based on T4 (or free T4 index) and TSH, the thyroidal state of the patient and the appropriateness of the reverse T3 determination were assigned. A total of 262 reverse T3 determinations were made in 246 patients. There is an inverse linear relationship between the log TSH and the reverse T3. patients with hypothyroidism plus illness may have a normal reverse T3 and patients with euthyroidism may have a low reverse T3. Reverse T3 is linearly related to bilirubin up to a bilirubin of approximately 171 microM (10 mg/dL). Sixty percent of the reverse T3 determinations were obtained for seemingly inappropriate indications. In association with a low free T4 index/T4, an unmeasurable reverse T3 did not lead to institution of thyroid hormone treatment in over 52% of cases. Although reverse T3 may be elevated in the setting of nonthyroidal illness, it is not reliable in distinguishing between the hypothyroid sick patient and the euthyroid sick patient. This is probably because of drug and disease effects on thyroid hormone metabolism as well as the presence of sufficient T4 substrate for conversion to reverse T3 in many hypothyroid sick patients.- - - - - - - - - - ranking = 2keywords = index (Clic here for more details about this article) |