Thyroid function tests in thyroid and nonthyroid disease

Nocturnal haemodialysis is associated with a reduced occurrence of low triiodothyronine serum levels in haemodialysed patients

Background

End-stage renal disease (ESRD) is associated with a broad spectrum of morphological and functional thyroid disorders. Recent studies have shown that low free triiodothyronine (fT3) levels are related to inflammatory status and endothelial activation in ESRD patients on haemodialysis (HD). Limited data exist about a possible relationship between dialysis regimen, namely long nocturnal haemodialysis (LNHD), and thyroid function parameters. The aim of this study was to evaluate the relationship between dialysis regimen and thyroid function, and consequently with the main patient outcomes.

Methods

To this purpose, we performed a retrospective, single-centre cohort study including 220 incident chronic HD patients treated during an 8-year period (from January 2010 to December 2017). The main clinical and haematochemical parameters, including thyroid function, were evaluated and related to the main patient outcomes.

Results

Patients with low fT3 levels (<3.05 ng/mL) showed significantly lower survival rates than patients with normal fT3 levels (>3.05 ng/mL) (P < 0.001), although there were no substantial differences in the demographic and clinical characteristics between the two groups. After propensity score 1:3 matching of 25 patients treated with nocturnal HD to 75 patients treated with diurnal HD, LNHD patients showed significantly higher survival rates (88.0% versus 61.3%, P = 0.001) and lower incidence of cardiovascular events than patients on diurnal dialysis (8.0% versus 40.0%, P = 0.001). Moreover, an 8-year time-dependent analysis showed that at any time, except for baseline, the rate of patients with fT3 levels >3.05 ng/mL was significantly higher in LNHD patients than in patients treated with diurnal dialysis.

Conclusions

Our data suggest that the application of alternative dialysis regimens, also reducing the frequency of low T3, could ameliorate outcomes and therefore reduce the incidence of cardiovascular events in HD patients.

Low T3 syndrome and long-term mortality in chronic hemodialysis patients

AIM: To investigate the predictive value of low freeT3 for long-term mortality in chronic hemodialysis (HD) patients and explore a possible causative role of chronic inflammation.

METHODS: One hundred fourteen HD patients (84 males) consecutively entered the study and were assessed for thyroid function and two established markers of inflammation, high sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6). Monthly blood samples were obtained from all patients for three consecutive months during the observation period for evaluation of thyroid function and measurement of inflammatory markers. The patients were then divided in two groups based on the cut-off value of 1.8 pg/mL for mean plasma freeT3, and were prospectively studied for a mean of 50.3 ± 30.8 mo regarding cumulative survival. The prognostic power of low serum fT3 levels for mortality was assessed using the Kaplan-Meier method and univariate and multivariate regression analysis.

RESULTS: Kaplan-Meier survival curve showed a negative predictive power for low freeT3. In Cox regression analysis low freeT3 remained a significant predictor of mortality after adjustment for age, diabetes mellitus, hypertension, hsCRP, serum creatinine and albumin. Regarding the possible association with inflammation, freeT3 was correlated with hsCRP, but not IL-6, and only at the first month of the study.

CONCLUSION: In chronic hemodialysis patients, low plasma freeT3 is a significant predictor of all-cause mortality. Further studies are required to identify the underlying mechanisms of this association.

Levels of cord blood thyroid stimulating hormone after external cephalic version

OBJECTIVE

To investigate the relationship between breech presentation, external cephalic version and levels of cord blood thyroid stimulating hormone.

DESIGN

Case-control study.

SETTING

University teaching hospital.

POPULATION

The study group consisted of 289 consecutive singleton deliveries at term over a four-year period, all of whom had an attempt at external cephalic version performed near term for breech presentation. The control group included 23,001 singleton term deliveries during the same four-year period.

METHODS

Between group differences were compared with the Mann-Whitney U test or chi2 test when appropriate.

MAIN OUTCOME MEASURES

Levels of cord blood thyroid stimulating hormone and the incidence of false positive screening results for congenital hypothyroidism.

RESULTS

Babies who were born vaginally after prior successful external cephalic version had significantly higher median levels of cord blood thyroid stimulating hormone (6.4 vs 6.0 mlU/L, P = 0.034) and the incidence of false positive screening for thyroid stimulating hormone (12.9% vs 7.2%, P = 0.016, OR 1.9) compared with babies with spontaneous cephalic presentation. In babies with a breech presentation born by elective caesarean section, previous attempts at external cephalic version had no effect on cord blood thyroid stimulating hormone levels. There was also no difference in the levels of cord blood thyroid stimulating hormone between cephalic and breech-presenting fetuses born by elective caesarean section. However, breech-presenting babies born by emergency caesarean section after onset of labour had higher median levels of cord thyroid stimulating hormone than those with cephalic presentation (5.1 vs 4.5 mIU/L, P= 0.008).

CONCLUSION

Levels of cord blood thyroid stimulating hormone are elevated in babies born vaginally after a successful external cephalic version. This finding may represent a biological difference in fetal response to the stress of labour in breech-presenting fetuses, which is not correctable by a successful external cephalic version.

Use of a single thyroxine test to evaluate ambulatory medical patients for suspected hypothyroidism

Previous recommendations for the use of thyroid function tests to diagnose patients with possible hypothyroidism have discounted the value of a total thyroxine (T4) test because many clinically hypothyroid patients have T4 levels that fall within the "normal" range. The authors examined the predictive value of a total T4 measurement in the evaluation of ambulatory general medical patients suspected of having hypothyroidism. Pregnant patients and those who were taking medications that interfere with thyroid homeostasis were excluded. Simultaneous T4 and thyrotropin (TSH) tests of 93 consecutive outpatients suspected to have hypothyroidism but found to be euthyroid and 27 patients discovered to be hypothyroid (TSH greater than 10 microU/ml) were examined. A T4 of 7.0 microliter/dl or less had a sensitivity of 93% with a false-positive rate of 19%. A T4 greater than 8.0 microgram/dl appeared to exclude hypothyroidism (negative posttest probability of 100%). It may be possible to achieve cost savings without loss of diagnostic accuracy by using a single total T4 measurement for the initial evaluation of suspected hypothyroidism in selected outpatients.

Hyperthyroidism in elderly women. Registered and detected by screening in a primary health care district

A laboratory screening for thyroid disease was performed among women older than 60 years in a primary health care district in a goiter region. The screening was combined with a questionnaire regarding previously treated thyroid disorder. A total of 1442 women i.e., 97.3% of the population studied were investigated. Through the laboratory screening we found 28 women (1.9%) with hyperthyroidism and they were successfully treated. Through the questionnaire 50 women (3.4%) were identified with previously treated hyperthyroidism--of these 42 were diagnosed after the age of 60. We suggest that physicians should maintain increased awareness to order thyroid laboratory tests (e.g. free T4 index, free T3 index) in women older than 60 years of age because atypical symptoms and signs are often difficult to separate from the age process per se.