Evaluation of the nocturnal serum thyrotropin (TSH) surge, as assessed by TSH ultrasensitive assay, in patients receiving long term L-thyroxine suppression therapy and in patients with various thyroid disorders

A mathematical algorithm to harmonize measurements for thyroid-stimulating hormone between instruments

BACKGROUND

Thyroid-stimulating hormone (TSH) is measured differently between diagnostic units using different devices, which makes cross-comparisons challenging. Here, we have developed a mathematical algorithm to harmonize TSH measurements between 2 instruments, the Abbott ISR2000 and the Siemens ADVIA Centaur XP.

METHODS

Applying the principle of the maximum allowable error between the standard curve and real signal values, the minimum number of comparison samples required for TSH hormone detection was calculated for both instruments. Next, a mathematical algorithm describing the relationship between TSH standard curves from both instruments was established. The algorithm was then tested on sample measurements from both instruments, with signals transformed to Siemens ADVIA Centuar XP-type data. Finally, test results were assessed where the relative error was 

RESULTS

Before conversion, the mean percentage error between the TSH results of samples measured on both instruments was 23.20% (>1/2 TEa). After algorithmic transformation, the average percentage error was reduced to 7.93% (<1/2 TEa).

CONCLUSIONS

Our algorithm enables TSH measurements across different instruments to be comparable, and provides a method to harmonize TSH data between laboratories that utilize different instrumentation.

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Key Words

• Comparability
• Conversion
• Determination
• Mathematical algorithm
• Thyroid-stimulating hormone (TSH)

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MESH Headings

• Humans
• Thyrotropin
• Algorithms

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Affiliation(s)

Xin Zhou Department of Laboratory Medicine, West China Hospital of Sichuan University, Chengdu 610041, China; Jintang First People's Hospital, Chengdu 610400, China
Zaishuan Liu Department of Laboratory Medicine, West China Hospital of Sichuan University, Chengdu 610041, China
Yining Ma College of Mathematics of Sichuan University, Chengdu 610065, China
Chongwei Zhang Department of Laboratory Medicine, West China Hospital of Sichuan University, Chengdu 610041, China
Yongkang Wu Department of Laboratory Medicine, West China Hospital of Sichuan University, Chengdu 610041, China; Jintang First People's Hospital, Chengdu 610400, China.

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Morning vs. bedtime levothyroxine administration: what is the ideal choice for children?

Background The present study compared the administration of levothyroxine (LT4) before breakfast and bedtime in school children diagnosed with hypothyroidism and analyzed the effects of timing on thyroid functioning and patient satisfaction. Methods A total of 163 children with acquired hypothyroidism (125 females and 38 males) between 8 and 18 years of age and taking LT4 for at least 3 months were enrolled in the study. The timing of administration of the drug of all subjects was shifted to bedtime. The levels of thyroid hormone and blood lipid, anthropometric measurements, Pediatric Quality of Life Inventory, Morisky Medication Adherence Scale and hypothyroidism symptoms scores were analyzed and compared at the beginning of the study and 3 months later after the shift in the timing of drug administration. Results There was no difference between the bedtime and morning regimens of LT4 with respect to thyroid hormone levels, quality of life, drug adherence and symptoms of hypothyroidism. At the end of the study, 45 of 70 new-onset treated subjects preferred the bedtime regimen. Also, drug adherence was found to be better in these patients. Conclusions We found no difference between the bedtime and morning regimens in both new-onset and long-standing treated patients. In naive patients, consideration of patient's preference for timing of drug administration may increase their adherence to medication. Therefore, we suggest that choice of drug administration timing should be based on the preference of patients.

Evaluation of adequacy of levo-thyroxine dosage in patients with differentiated thyroid carcinoma: correlation between morning and afternoon TSH determination

PURPOSE

The aim of this study was to judge the reliability of evaluating thyroid-stimulating hormone (TSH) and free thyroxine (f-T4) in the morning and afternoon in differentiated thyroid carcinoma (DTC) patients.

METHODS

We evaluated 153 DTC patients, aged 61 ± 13 years, in active follow-up in our center after primary treatments and under stabilized levo-thyroxine (L-T4) posology. In each patient, morning and afternoon examinations were performed 1-3 months apart. Blood samples were collected at 08:00-09:00 h and 15:00-16:00 h. TSH and f-T4 were evaluated in both samples. Thyroglobulin (Tg), Tg-antibodies and neck ultrasonography were also evaluated.

RESULTS

According to clinical and laboratory examinations, 92% of patients were disease-free, 6% had biochemical disease, and 2% structural disease. L-T4 dosages (1.64 ± 0.38 µg/kg b.w.) proved the same on both occasions, despite slight changes in body weight or L-T4 posology in 15% of patients. Free-T4 values were significantly higher in the afternoon (21.5 ± 0.3 pmol/L) than in the morning (18.8 ± 0.4 pmol/L; P < 0.0001), whereas TSH values were statistically unchanged (morning 0.85 ± 0.25 mIU/L; afternoon 0.72 ± 0.20 mIU/L). There was a significant correlation (P < 0.0001) between the two TSH determinations in the same patients.

CONCLUSIONS

In DTC patients, follow-up examination consists of clinical and laboratory evaluations. The majority of patients have good disease control. Our study suggests that the adequacy of L-T4 therapy can be monitored equally well either in the morning or in the afternoon. Afternoon examinations can alleviate crowding in hospital ambulatories in the morning.

MECHANISMS IN ENDOCRINOLOGY: Impact of isolated TSH levels in and out of normal range on different tissues

Routine treatment of thyroid cancer (TC) includes long-term suppression of TSH. The necessity of this treatment in low- and intermediate-risk patients as well as the extent of TSH suppression is currently under discussion. A literature search was performed to illustrate the role of TSH in extrathyroidal cells and to identify potential reasons for different effects of exogenously suppressed and endogenously low TSH levels. Although adverse effects of subnormal and supranormal TSH blood levels on heart and brain have not been consistently found, studies show a clear negative effect of suppressed TSH levels on bone mineral density. Experimental data also support an important role of TSH in the immune system. The ability of levothyroxine (l-T4) to regulate TSH levels and triiodothyronine levels in a physiological manner is limited. Reduction of circadian changes in TSH levels, decrease of thyroid hormone-binding proteins, prevention of potential compensatory increases of TSH levels (e.g., in old age), and unresponsiveness of TSH-producing cells to TRH on l-T4 treatment might cause adverse effects of suppressed TSH levels. In view of the adverse effects of aggressive TSH suppression, achieving the suggested levels of TSH between 0.9 and 1 mU/l in the treatment of low-to-intermediate risk TC patients appears justified.

Controversies in the management of hypothyroidism during pregnancy

IMPORTANCE

In the last 3 years, we have witnessed the publication of multiple but conflicting guidelines on the management of hypothyroidism during pregnancy. Hypothyroidism is one of the most common endocrinopathies in reproductive-age and pregnant women. Given the prevalence of thyroid disease, it is highly likely that obstetricians will encounter and provide care for pregnant women with thyroid disease. Therefore, a review of current guidelines and management options is clinically relevant.

OBJECTIVES

Our goals are to review the changes in thyroid function during pregnancy, the options for testing for thyroid disease, the different categories of thyroid dysfunction and surveillance strategies among subspecialty societies, and the obstetric hazards associated with thyroid dysfunction and review the evidence for benefit of treatment options for thyroid disease.

EVIDENCE ACQUISITION

We reviewed key subspecialty guidelines, as well as current and ongoing studies focused on the treatment of hypothyroidism during pregnancy.

RESULTS

There are significant differences in the identification and management of thyroid disease during pregnancy among subspecialists. We present our recommendations based on the available evidence.

RELEVANCE

Evidence exists that obstetricians struggle with the diagnosis and treatment of hypothyroidism. According to recent surveys, the management of hypothyroidism during pregnancy is the number 1 endocrine topic of interest for obstetricians. A synopsis of recently published subspecialty guidelines is timely.

CONCLUSIONS

Recent, evidence-based findings indicate that obstetricians should consider modifying their approach to the identification and treatment of thyroid disease during pregnancy.

Changes in Serum TSH and T4 Levels after Switching the Levothyroxine Administration Time from before Breakfast to before Dinner

Background. Levothyroxine is commonly used in the treatment of patients with hypothyroidism. Levothyroxine is most often administered in the morning, on an empty stomach, in order to increase its oral absorption. However, many patients have difficulties taking levothyroxine in the morning. Aim. The aim of this study was evaluating the effect of changing levothyroxine administration time from before breakfast to before dinner on the serum levels of TSH and T4. Subjects and Methods. Fifty patients between 18 and 75 years old with hypothyroidism were included in the study and were randomly divided into two groups. Each group received two tablets per day (one levothyroxine tablet and one placebo tablet) 30 minutes before breakfast and 1 hour before dinner. After two months, the administration time for the tablets was changed for each group, and the new schedule was continued for a further two-month period. The serum TSH and T4 levels were measured before and after treatment in each group. Results. Changing the levothyroxine administration time resulted in 1.47 ± 0.51 µIU/mL increase in TSH level (p = 0.001) and 0.35 ± 1.05 µg/dL decrease in T4 level (p = 0.3). Conclusions. Changing the levothyroxine administration time from before breakfast to before dinner reduced the therapeutic efficacy of levothyroxine.

Diurnal thyrotropin secretion in short-term profound primary hypothyroidism: does it ever persist?

Circulating serum thyrotropin (TSH) levels in euthyroid humans show a definite circadian variation, which is maintained in both mild hyperthyroidism and mild hypothyroidism. Yet conflicting data exist with regard to whether this variation persists in at least some patients with severe primary hypothyroidism. We, therefore, studied the diurnal variation in serum TSH in 10 patients (age range 20 to 84 years) with a history of thyroid failure due to prior total thyroidectomy and radioiodine (RAI) ablative treatment performed for thyroid cancer after short-term discontinuation of thyroid hormone (TH) therapy. Serum TSH was measured hourly for a 24-hour period. All data were normalized by converting the TSH values to a percentage (%), designating the 11:00 hour value as 100% (baseline). The average serum TSH levels were markedly elevated in all patients. There was no statistically significant difference between the TSH % values at any time during the 24-hour period when compared with baseline. Further, cosine regression analysis showed absence of rhythmicity in TSH % values over time; notably, no patient showed a variation in TSH % values > or = 15% of baseline. In conclusion, diurnal rhythmicity in serum TSH levels was abolished in a uniform cohort of patients with short-term severe primary hypothyroidism. We speculate that the complete lack of peripheral negative feedback input to the hypothalamus or pituitary or both may override the central rhythm-sustaining influences on TSH secretion.

Diagnosis of thyroid dysfunction: present and future

Thyroid disorders represent the second most common endocrine disorder after diabetes mellitus. For this reason, investigation of thyroid function is frequently carried out, taking advantage of numerous tests currently available. It it the physicians's difficult task to select the most appropriate assay(s) in the different pathophysiological conditions from the bewildering array of thyroid function tests, in order to satisfy optimal diagnostic standards, but also to fulfill cost/benefit criteria. Aim of this paper is to provide a brief overview of advantages and disadvantages of main thyroid function tests, and to suggest a testing strategy for the diagnosis of suspected thyroid dysfunction.

Lack of seasonal variation in abnormal TSH secretion in patients with seasonal affective disorder

The circadian variations in thyroid-stimulating hormone (TSH) secretion, with particular attention to the nocturnal serum TSH surge and the TSH response to thyrotropin releasing hormone (TRH), were measured in seven patients with seasonal affective disorder (SAD) and in eight normal controls. Both patients with SAD and normal controls were tested in fall/winter, when patients were suffering depressive symptoms, and in spring/summer, when patients were euthymic. The TRH tests were performed in the morning. In all tests, the mean peak TSH response to TRH was significantly lower in the patients with SAD than in the normal controls. No significant differences were observed in either group between spring/summer and fall/winter tests. At both periods, patients with SAD showed normal TSH levels in the morning, but did not experience a nocturnal TSH surge. In this group, morning and night TSH levels were similar. In contrast, normal controls showed significantly higher TSH levels at night than in the morning. Serum-free thyroid hormone levels were in the normal range in all subjects. Morning and night serum cortisol levels and 24-hour urinary cortisol concentrations were similar in all subjects. These data show that the secretion of TSH is impaired in SAD, regardless of the phase of the psychiatric disease. The low TSH response to TRH in the presence of normal serum thyroid hormone levels and the lack of the TSH nocturnal surge suggest that patients with SAD might be affected by mild central hypothyroidism.

Fatal nonthyroidal illness may impair nocturnal thyrotropin levels

PURPOSE

This study was undertaken to assess whether circadian variation of thyrotropin (TSH) is affected by the severity of a nonthyroidal illness.

PATIENTS AND METHODS

On the second day of admission to a medical intensive care unit, 20 consecutive patients with the major diagnosis of acute respiratory failure underwent TSH measurements at 8 A.M., 9 P.M., 11 P.M., and 1 A.M., with two sensitive assays.

RESULTS

Six patients died, five of whom had hypothyroxinemia (thyroxine [T4] less than 5.5 micrograms/dL) (83%) on the day of the study, whereas only three of the 14 survivors had low T4 (21%; p less than 0.05). Baseline 8 A.M. TSH measured with the two assays was similar in both groups and there was a progressive increase in TSH in survivors and a decrease in nonsurvivors at 9 P.M. and 11 P.M. However, the difference at these time points was not statistically significant. At 1 A.M., TSH levels were significantly lower among nonsurvivors (0.75 +/- 0.34 microU/mL with assay 1, and 0.7 +/- 0.4 microU/mL with assay 2) than in survivors (2.3 +/- 0.46 microU/mL with assay 1, and 2 +/- 0.5 microU/mL with assay 2; p less than 0.005; Wilcoxon test). Five of the nonsurvivors and none of the survivors had a suppressed 1 A.M. TSH level (p less than 0.001), suggesting a good correlation between suppressed 1 A.M. TSH and mortality. After exclusion of patients receiving drugs known to affect TSH levels (two nonsurvivors and four survivors), the same dissociation in TSH changes was observed, and significantly lower 1 A.M. TSH levels were observed in nonsurvivors than in survivors (0.13 +/- 0.08 microU/mL versus 2.7 +/- 0.6 microU/mL with assay 1; p less than 0.01). Cortisol levels were significantly higher only at 8 A.M. in nonsurvivors whether patients receiving drugs were included in the analysis (41.6 +/- 3.2 versus 28.4 +/- 2.7 micrograms/dL; p less than 0.01) or not (45.3 +/- 4.6 versus 30.5 +/- 3.6 micrograms/dL; p less than 0.01). At other times, cortisol levels were similar in both groups. The 24-hour TSH areas under the curve were also lower in nonsurvivors than in survivors whether patients receiving drugs known to affect TSH levels were included or not. However, cortisol areas under the curve were similar in both groups.

CONCLUSION

It is concluded that fatal illness is associated with a suppression of the late night TSH surge.

Thyroxine uptake by human hepatoma cells from serum of patients submitted to long-term thyroxine suppressive therapy

The significance of thyroxine (T4) uptake from serum in the assessment of thyroid status was evaluated, using human hepatoma (Hep G2) cells, in 30 euthyroid subjects, 6 hypothyroid and 19 hyperthyroid patients, and in 23 athyreotic cancer patients under T4 suppressive therapy. Cellular thyroxine (CT4) was determined according to Sarne and Refetoff, J. Clin. Endocrinol. Metab. 61: 1046, 1985. CT4 averaged 9.9 +/- 2.8 pg/well (mean +/- SD, range 5.7-15.3) in euthyroid subjects, 1.5 +/- 1.0 pg/well (range 0.05-4.2) in hypothyroid patients, 40.5 +/- 18.8 pg/well (range 18.3 +/- 104.7) in hyperthyroid patients, and 23.7 +/- 7.2 pg/well (range 14.2-40.2) in T4-treated patients. In eu-, hypo- and hyperthyroid patients, a significant correlation was observed between CT4 and free T4 index (FT4I), free T4 (FT4) or Sex Hormone Binding Globulin (SHBG) values. In T4-treated patients, CT4 values were correlated with FT4I values, but not with FT4 or SHBG levels. All T4-treated patients with elevated SHBG levels had elevated FT4, FT4I and CT4 values. In contrast, of the 16 T4-treated subjects with normal serum SHBG concentrations, all but one had normal FT3, 3 (19%) had elevated FT4, 10 (62%) elevated FT4I and 13 (81%) elevated CT4, but all (100%) had undetectable TSH levels. Thus, considering serum SHBG concentrations as a parameter of hepatic tissue response to thyroid hormone, CT4 values, at least in T4-treated patients, do not accurately reflect the liver responsiveness to thyroid hormone action.