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[Thyroid function tests in a sample of hospitalized patients].

In a sample of hospitalized patients, serum levels of T3, T4 and TSH were measured on the next day after admission. We included 26 patients admitted to Internal Medicine ward (group I) and 27 patients admitted to the intensive care unit (group II), comparing the results with those of 25 normal volunteers (group I). Mean values of T3 and T4 tend to be lower in patients than in healthy subjects, especially in those patients more aggravated, but differences were not statistically significant. In group II there were 5 patients with low T3, 4 with low T4 and two with both alterations. In group III, two patients had low T3, three had low T4 and 10 had both low T3 and low T4. The ratio between normal and abnormal results was significantly different between sick and healthy individuals, and between patient in the intensive care unit and the Internal Medicine ward, suggesting a correlation with gravity. 52.8% of patients hospitalized studied showed almost one alteration in the thyroid function tests.

Humans↗
PubMed2003

Thyroid function tests and neurocognitive functioning in children referred for attention deficit/hyperactivity disorder.

BACKGROUND: Thyroid abnormalities have been associated with attention deficit/hyperactivity disorder (ADHD) and with other childhood psychiatric disorders. The goal of this study was to determine the relationships between thyroid hormone concentrations, neurocognitive functioning, and psychiatric diagnosis in children. METHODS: Free thyroxine index (FT4I) and thyroid stimulating hormone (TSH) were obtained, along with diagnostic and descriptive information for 338 children referred to a clinic specializing in learning and behavior problems. RESULTS: Thyroid abnormalities were uncommon in children referred for ADHD. After excluding children with thyroid disease, there was a greater proportion with low concentrations of normal FT4I for ADHD-Predominantly Inattentive type (ratio=7.0), but not for ADHD-Combined Type. High concentrations of normal FT4I were associated with mood lability, preoccupations, and lower ratings of attention problems. Thyroxine concentrations within the normal range were differentially associated with ADHD-Combined Type compared to ADHD-Predominantly Inattentive, mood disorders, and pervasive developmental disorders. CONCLUSION: Thyroxine concentrations were associated with mood symptoms and unusual behaviors, and were less strongly related to attentional functioning. Thyroxine concentrations were not related to hyperactivity.

Adolescent↗
PubMed1986

Thyroid function tests in acutely ill patients. Comparison of analogue based free thyroid hormone assays with free thyroxine index.

A prospective study of 100 acutely ill patients was carried out to assess the value of the free thyroxine (FT4) assay as a replacement screening procedure for the free thyroxine index (FTI). We found that the FT4 assay was significantly influenced by the albumin concentration, so that the number of follow-up tests required increased markedly. This was especially true at the low end of the FT4 range where the need for thyrotropin assays increased by 162%. The free triiodothyronine (FT3) assay was also shown to be albumin dependent. It is not useful to replace one set of difficulties due to protein binding with another, and overall it was concluded that it is not cost-effective to screen hospital patients for thyroid dysfunction using free hormone assays based on labelled analogue techniques.

Humans↗
PubMed2005

Analytic bias of thyroid function tests: analysis of a College of American Pathologists fresh frozen serum pool by 3900 clinical laboratories.

CONTEXT: In proficiency testing surveys, there are differences in the values reported by users of various analytic methods. Two contributors to this variation are calibrator bias and matrix effects of proficiency testing materials. OBJECTIVES: (1) To quantify the biases of the analytic methods used to measure thyroid-stimulating hormone, thyroxine, triiodothyronine, free thyroxine, and free triiodothyronine levels; (2) to determine if these biases are within allowable limits; and (3) to ascertain if proficiency testing materials correctly identify these biases. DESIGN: A fresh frozen serum specimen was mailed as part of the 2003 College of American Pathologists Ligand and Chemistry surveys. The means and SDs for each analytic method were determined for this sample as well as for a proficiency testing sample from both surveys. In the fresh frozen serum sample, target values for thyroxine and triiodothyronine were determined by isotope dilution/liquid chromatography/tandem mass spectrometry. All other target values in the study were the median of the means obtained for the various analytic methods. MAIN OUTCOME MEASURES: Calibration biases were calculated by comparing the mean of each analytic method with the appropriate target values. These biases were evaluated against limits based on intra- and interindividual biological variation. Matrix effects of proficiency testing materials were assessed by comparing the rank of highest to lowest analytic method means (Spearman rank test) for each analyte. PARTICIPANTS: Approximately 3900 clinical laboratories were enrolled in the College of American Pathologists Chemistry and Ligand surveys. RESULTS: The number of methods in the Ligand Survey that failed to meet the goals for bias was 7 of 17 for thyroid-stimulating hormone and 11 of 13 for free thyroxine. The failure rates were 12 of 16 methods for thyroxine, 8 of 11 for triiodothyronine, and 9 of 11 for free triiodothyronine. The means of the analytic method for the proficiency testing material correlated significantly (P < .05) only with the fresh frozen serum means for thyroxine and thyroid-stimulating hormone in the Chemistry Survey and free triiodothyronine in the Ligand Survey. CONCLUSIONS: A majority of the methods used in thyroid function testing have biases that limit their clinical utility. Traditional proficiency testing materials do not adequately reflect these biases.

Calibration↗
PubMed1989

Effects of chronic peritoneal dialysis on thyroid function tests.

Peritoneal dialysis is associated with large losses of protein. In order to quantify thyroid hormone excretion in the dialysate and to examine the possibility that peritoneal dialysis may result in clinical hypothyroidism, nine endstage renal disease (ESRD) patients undergoing either continuous ambulatory peritoneal dialysis (CAPD) or chronic intermittent peritoneal dialysis (IPD) were studied. Total protein excretion in the peritoneal fluid was 21.5 +/- 2.1 g/24 h and did not vary with the mode of peritoneal dialysis. Thyroid binding globulin (TBG) excretion was 6.4 +/- 1.3 mg/24 h, higher than the values reported in the literature for urinary TBG excretion in patients with the nephrotic syndrome. Despite the higher TBG losses, serum TBG remained in the normal range. Mean peritoneal total T4 and T3 were 8.1 +/- 1.6 micrograms/24 h and 89.5 +/- 14.6 ng/24 h, and there was a significant correlation between peritoneal T4 and TBG (r = 0.69; P less than 0.01) and between peritoneal total proteins and T4 (r = 0.80; P less than 0.001). Despite the finding that large amounts of protein are lost in peritoneal fluid, T4 and T3 losses were relatively modest and remained below their daily production rates, and none of the patients were overtly hypothyroid. Serum thyroid stimulating hormone (TSH) was mildly elevated in three of nine patients and was consistent with early thyroid failure. The patients' serum iodine levels were higher than normal but did not predict the patients' thyroid status. We conclude that major protein losses could predispose patients undergoing CAPD to thyroid failure and that long-term follow-up of thyroid function is warranted in these patients.

Aged↗
PubMed1996

An algorithmic approach to thyroid function testing in a managed care setting. 3-year experience.

An algorithm (directed thyrotropin [TSH], directed thyroid testing algorithm [DRTSH]) for the initial evaluation and monitoring of thyroid function was established in our institution in 1990. The algorithm begins with measurement of TSH by a sensitive immunoassay. If TSH is either < 0.4 mU/L or > 5.5 mU/L, a free thyroid index (T4 x Resin Uptake Ratio (RU)) is automatically performed on the same sample on the same day. In the setting of a large, predominately outpatient, prepaid health care population, the algorithm reduces unnecessary testing and focuses resources on the patients who need it. Three years after its introduction, physician acceptance of this approach is high ( > 90%), test utilization is reduced, test turnaround time is reduced, and significant cost-savings can be demonstrated.

Algorithms↗
PubMed1985

Circannual and within-individual variation of thyroid function tests in normal subjects.

Blood was taken from normal subjects at monthly intervals over a period of one year for subsequent determination of serum thyroid hormone concentrations. Thyroid-stimulating hormone (TSH) responses to TSH-releasing hormone were performed at 3-monthly intervals. This study provided data on within-individual variation and on seasonally-related changes of these thyroid function tests. The results showed that, within an individual, thyroid hormone concentrations are maintained within narrow limits. For both thyroxine and triiodothyronine the component contribution of within-individual variation to the population-based variation (the latter also termed the 'reference interval', or colloquially the 'normal range') was small. This high degree of individuality implies that rigorous comparison of thyroid hormone results against a population-based 'normal range' can be potentially misleading. Despite the limited within-individual variation, seasonally-related changes in thyroid hormone concentrations were apparent, with higher thyroxine and triiodothyronine values seen in winter months. A tendency to a greater TSH response to TSH-releasing hormone was also noted at this time. Conceivably these changes could reflect a centrally-mediated response of the hypothalamic-pituitary-thyroid axis to environmental temperature.

Biological Clocks↗