Nonthyroidal illness

TSH 0.S-2.S milliunits/L (0.5-2.5 microunits/mL)a Gold standard may be lowered by dopamine, dopamine agonists, glucocorticoids, octreotide, recovery from severe nonthyroidal illness... 

Langton JE, Brent GA. Nonthyroidal illness syndrome Evaluation of thyroid function in sick patients. Endocrinol Metab Clin North Am 2002 31 159-172. 

B45. Brent, G. A., and Hershman, J. M Thyroxine therapy in patients with severe nonthyroidal illness and low serum thyroxine concentration. J. Clin. Endocrinol. Metab. 63, 1-8 (1986). 

C16. Chopra, I. J., Sakane, S., and Chua Teco, G. N., A study of the serum concentration of tumor necrosis factor-a in thyroidal and nonthyroidal illness. J. Clin. Endocrinol. Metab. 12, 1113-1116(1991). 

D24. Docter, R., van Toor, H., Krenning, E. P., de Jong, M., and Hennemann G., Free thyroxine assessed with three assays in sera of patients with nonthyroidal illness and of subjects with abnormal concentrations of thyroxine-binding proteins. Clin. Chem. 39,1668-1674 (1993). 

M24. Mendel, C. M., Laughton, C. W., McMahon, F. A., and Cavalieri, R. R., Inability to detect an inhibitor to thyroxine-serum protein binding in sera from patients with nonthyroidal illness. Metabolism 40, 152-159 (1991). 

W18. Wong, T. K., and Hershman, J. M., Changes in thyroid function in nonthyroid illness. Trends Endocrinol. Metab. 3, 8-12 (1992). 

Nonthyroidal illness (HIV infection, infectious and chronic active hepatitis, estrogen-producing tumors, acute intermittent porphyria)... 

Nonthyroidal illness (major illness or surgical stress, nephrotic syndrome)... 

As patients recover from NTIs, many of the thyroid test abnormalities revert to normal. Total T4 concentrations will be corrected first followed by a rise in T3. Serum TSH may also transiently rebound to high concentrations for several days or weeks before returning to normal. Thus, in NTI, abnormal thyroid function test results do not necessarily indicate the presence of thyroid disease, but may demonstrate adaptations to the catabolic state. Conversely, paradoxically normal values may be seen in patients with thyroid disease as a result of medications or nonthyroidal illness per se. Assessments of thyroid function in ill patients are best postponed until the illness resolves, unless a diagnosis would affect patient outcome. 

Immunometric methods based on chemiluminescence are capable of measuring TSH at concentrations required to accurately detect the low concentrations of serum TSH found in patients with true hyperthyroidism or the suppressed concentrations fmmd in patients with nonthyroidal illnesses. These sensitive methods resulted from the appHca-tion of the immunometric sandwich configuration, in which a serum TSH molecule forms a bridge between two or more... 

The THBR is derived from a version of the T3 or T4 uptake test. Uptake tests are used to estimate the number of unoccupied (unsaturated) thyroid hormone bindhig sites on serum proteins. This information is important because variations in total thyroid hormone concentrations in blood, as discussed previously, have resulted from changes in binding protein concentrations. Values obtained by uptake methods are expressed as a THBR, which is directly proportional to the free hormone fraction (within limits). Measurement of THBR, in conjunction with a total hormone concentration, is a clinically useful indirect method for calculating the FT4 (or FT3) index. The index approach is particularly useful in patients with nonthyroidal illness in whom FT4 immunoassay methodologies are unreliable. Specifically, TT4 measurement is more diagnostically useful in such patients provided that values are interpreted in accord with the severity of illness in the patient that is indirectly reflected by abnormalities in THBR. 

Ekins R. Free triiodothyronine in nonthyroidal illness ILetter]. Cfin Chem 1994 40 162-3. 

Y. Suzuki, M. Nanno, R. Gemma, T. Yoshimi, Plasma free fatty acids, inhibitor of extrathyroidal conversion of T4 to T3 and thyroid hormone binding inhibitor in patients with various nonthyroidal illness,Endocrinol Jpn 39, 445-53 (1992). 

A wide variety of abnormalities of pituitary-thyroid function, serum thyroid hormone binding, and extrathyroidal thyroid hormone metabolism occur in patients with nonthyroidal illness. These abnormalities frequently result in decreased serum T3 concentrations and less often lead to a decreased serum T4 concentration. Serum TSH concentrations are usually within the normal range. The presence of coexisting primary hypothyroidism can be recognized in patients who have other illnesses by an elevation in the TSH concentration. 

The degree and extent of the abnormality in thyroid function generally correlates with the severity of the nonthyroidal illness. These conditions are frequently referred to as the euthyroid sick syndrome. It is likely that these changes represent adaptive forms of hypothyroidism that serve to reduce the availability of thyroid hormones to lessen the impact of the nonthyroidal Ulness. ... 

To confuse matters, some patients with nonthyroidal illness have elevation of their serum T4 concentration. Most commonly, this is seen in patients with psychiatric disorders during acute psychotic breaks. Thyroid hormone levels return to normal within 2 weeks after snccess-ful treatment of the underlying psychiatric disease. The occnrrence of these abnormalities requires that care be taken in diagnosing hypothyroidism or hyperthyroidism in patients who have nonthyroidal illnesses. 

A major determinant of postnatal T4 levels is nonthyroidal illness (Simpson et at, 2005) 75% of infants <28 weeks gestation are characterized as severely ill, as defined by the British Association of Perinatal Medicine (BAPM), level 1 (Simpson et al., 2005), whereas only 15% of infants 28—30 weeks gestation are so categorized. 

Reported in elderly subjects with and without possible defective organification and autoimmune thyroiditis Chronic nonthyroidal illness Cystic fibrosis... 

Usually elevated serum TSH levels and low T4 levels are enough to diagnose primary hypothyroidism in aged people, however, thyroid function tests may be affected by the ageing process, nonthyroidal illnesses and drugs. 

From a theoretical point of view, therapeutic strategies that can be employed to optimize TH signaling in the presence of HF and nonthyroidal illness syndrome can be summed up in the following five points ... 

Abnormalities in thyroid function tests may be encountered in a variety of severe nonthyroidal illnesses, either acute or chronic, and some of the abnormalities are mediated through decreases in TBPA or in TBG, or in both binding proteins. Where the abnormality is due only to decrease in TBG and TBPA, the FTI, FTC, and similar measurements are normal but total T4 in serum is low and the resin uptake of T3 is elevated. This is the situation in chronic renal disease and although the FTI and similarly calculated free T4 factors do not give normal results in all patients, the free T4 concentration is normal in nearly all euthyroid patients (J3). 

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