Do nonesterified fatty acids displace thyroxin from its plasma binding sites in severe nonthyroidal illnesses?

Abstract

Severe nonthyroidal illnesses have been associated with increases in nonesterified fatty acids (NEFA) and the dialyzable fraction of thyroxin (T4) in plasma. We have further investigated their possible relationship in severe nonthyroidal illnesses as well as in induced in vivo and in vitro situations involving increased NEFA. We demonstrate that there is no relationship between NEFA and the dialyzable fraction of T4, either in severe nonthyroidal illnesses or in the other situations, unless plasma NEFA concentrations exceed 5 mmol/L in normal persons or 1.7 mmol/L in nonthyroidal illnesses, and that this concentration was not reached in the patients we studied, with one exception. We conclude that NEFA are unlikely to contribute to an inhibition of the binding of T4 to the binding proteins that might be present in plasma of patients with severe nonthyroidal illnesses unless their NEFA concentrations are very high.

Labelled antibody-based one-step time-resolved fluoroimmunoassay for measurement of free thyroxine in serum

“…However, NEFA concentrations increased from 0.4 to 2.1 mmol/L after storage of samples at 4°C. 33 Thus, in order to investigate the robustness of FT4 assay to increases in NEFA, the experimental addition of NEFA in this proposed FT4 assay is of importance when inappropriate storage and handling of samples may be taken into account. As shown in Figure 6, up to 2.5 mmol/L concentration of oleic acid would cause only about 7% increase in FT4.…”

Διερεύνηση Χημικής Τροποποίησης Ενζύμων Για Την Ανάπτυξη Ανοσοενζυμικής Μεθοδολογίας

“…5) Οι υψηλές συγκεντρώσεις μη εστεροποιημένων λιπαρών οξέων (NEFAs) που παρεμποδίζουν τη σύνδεση των θυρορμονών με τις πρωτεΐνες του ορού (Nicolson et al, 1989).…”