Persistence of elevated TSH levels despite large doses of L-thyroxin is not uncommon, although thyroxin substitution is usually easy and convenient. The first cause to be considered is thyroxin malabsorption, whether organic, due to concomitant gastric or intestinal disease, or bariatric surgery, or, more frequently, related to dietary or drug interference. Proton-pump inhibitors, antacids and a long list of drugs may decrease thyroxin absorption. Drugs and thyroid disruptors may also affect thyroid hormone metabolism at many levels. Factitious disease, the so-called pseudo-malabsorption, is related to poor patient compliance, a difficult diagnosis which can be confirmed by a L-thyroxin absorption test. Whether patient education, as well as the method of education, is beneficial in this condition remains to be clarified. The recent advent of generic preparations of L-thyroxin is to be taken into consideration since the absorption or the quality of some preparations might be questionable. Finally, still another concept is of importance. Indeed, thyroid function parameters in healthy subjects may show considerable inter-individual variability indicating that each individual has a unique set point of thyroid function. In addition to clinically parameters such as body mass index, genetic factors, some directly involved in thyroid hormone metabolism, are important determinant of the pituitarythyroid axis homeostasis.
30 Apr - 04 May 2011
European Society of Endocrinology