triiodothyronine--reverse and Protein-Energy-Malnutrition

Despite the widespread interest in malnutrition in the elderly, the utility of laboratory tests is limited. This is because their diagnostic significance can be impaired by undercurrent diseases, pre-analytical effects and unsatisfactory standardization. This survey summarizes the most important parameters of malnutrition. Thus, "nitrogen balance" is considered the golden standard of nutrition status, while the diagnostic significance of serum proteins depends on their biological half-time. Albumin is seen as the most reliable malnutrition marker, but cholinesterase and cholesterol-decrease must also be mentioned. The so-called "low-T3-phenomenon" which is caused by the production of "reverse T3", seems to be the unique parameter for the "catabolic" state of metabolism. Of special interest are also prognostic markers of mortality, such as orosomucoid. Cytokines, other signal peptides, trace elements and vitamins are from the diagnostic point of view of rather limited significance. In sum, the diagnosis and monitoring of malnutrition in the elderly represents an important challenge for laboratory medicine.

Topics: Aged; Blood Proteins; Cholesterol; Comorbidity; Energy Metabolism; Humans; Nitrogen; Nutrition Assessment; Protein-Energy Malnutrition; Trace Elements; Triiodothyronine; Triiodothyronine, Reverse; Vitamins

A man with diabetes mellitus, chronic hepatitis, chronic pancreatitis, and blind loop syndrome but without any previous thyroid disease developed three episodes of transient primary hypothyroidism associated with protein-calorie malnutrition (PCM). Clinical examinations suggested that this primary hypothyroidism was not caused by chronic thyroiditis, iodine deficiency, or iodine excess. Since the three times association of primary hypothyroidism with PCM suggested the possibility that the primary hypothyroidism was caused by PCM, we have tried to clarify its mechanism. For this purpose we have investigated the change of thyroid functions during protein-calorie repletion and the effect of amino acid deficiency. Total parenteral nutrition with full supplementation of amino acids resulted in a rapid increase in serum thyroxine (T4), triiodothyronine (T3), free T4, and reverse T3, and subsequently, a rapid decrease in TSH in several days after the nutrition was begun. When amino acid solution was changed to that depleted of phenylalanine and tyrosine after the restoration of thyroid functions, serum T4 and T3 showed a gradual decrease, but serum free T4 and TSH remained within normal range. However, resupplementation of phenylalanine and tyrosine after 8 weeks of depletion gave a rapid increase in serum T4, T3, free T4, and reverse T3. These results suggested that the primary hypothyroidism was caused by an impaired T4 production and that the deficiency of amino acids in PCM partly contributed to the impairment of T4 production.

Topics: Aged; Amino Acids; Humans; Hypothyroidism; Male; Parenteral Nutrition, Total; Phenylalanine; Protein-Energy Malnutrition; Thyroid Function Tests; Thyrotropin; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse; Tyrosine