Thyroid-Stimulating Hormone Reference Ranges in the First Trimester of Pregnancy in an Iodine-Sufficient Country

BACKGROUND

Thyroid dysfunction is associated with negative neonatal and obstetric outcomes. Large differences in thyroid function reference intervals exist across different populations. These differences can be explained by population-specific factors, such as iodine status. Many countries in Latin America report iodine sufficiency, but relatively few countries have published up-to-date data on iodine levels and thyroid function in the overall population, and especially in pregnant women. We evaluated the iodine status of pregnant women in Chile and determined thyroid hormone reference ranges in this population.

METHODS

This was a prospective observational study of healthy Chilean women at their first prenatal visit before week 14. Thyroid-stimulating hormone (TSH), total thyroxine (T₄), free T₄, antithyroid peroxidase antibody (TPOAb), and iodine levels from spot urine samples were measured. Iodine status and the reference ranges for TSH were calculated.

RESULTS

A total of 1,022 pregnant women in the first trimester were selected. Urinary iodine levels were measured in 302 randomly-selected women. The median urinary iodine concentration was 173.45 μg/L (interquartile range, 108.11 to 249.35).The reference ranges of TSH were calculated in 670 patients selected according to the National Academy of Clinical Biochemistry guidelines. The median TSH level was 1.88 μIU/mL (2.5th percentile: 0.13 to 97.5th percentile: 5.37). Using the reference range in the 1,022 women, the prevalence of clinical hypothyroidism was 1.76%, and that of subclinical hypothyroidism was 3.92%. TPOAb positivity was more common in women with TSH levels above 3.5 μIU/mL.

CONCLUSION

We found adequate iodine intake and a right-shifted distribution of serum TSH levels in pregnant women in Chile. The prevalence of hypothyroidism in our sample of pregnant women was higher than has been described in the literature.

Early pregnancy thyroid hormone reference ranges in Chilean women: the influence of body mass index

OBJECTIVE

Thyroid dysfunction and obesity during pregnancy have been associated with negative neonatal and obstetric outcomes. Thyroid hormone reference ranges have not been established for the pregnant Hispanic population. This study defines thyroid hormone reference ranges during early pregnancy in Chilean women and evaluates associations of body mass index (BMI) with thyroid function.

DESIGN, PATIENTS, MEASUREMENTS

This is a prospective observational study of 720 healthy Chilean women attending their first prenatal consultation at an outpatient clinic. Thyroid function [TSH, Free T4, Total T4 and antithyroid peroxidase antibodies (TPOAb)] and BMI were assessed at 8·8 ± 2·4 weeks of gestational age.

RESULTS

Median, 2·5th percentile (p2·5), and 97·5th percentile (p97·5) TSH values were higher, while median, p2·5, and p97·5 free T4 values were lower in obese patients compared with normal weight patients. Obesity was associated with a median TSH 16% higher (P = 0·035) and a median free T4 6·5% lower (P < 0·01) than values from patients with normal weight. BMI had a small, but statistically significant effect on TSH (P = 0·04) and free T4 (P < 0·01) when adjusted by maternal age, TPO antibodies, parity, sex of the newborn, gestational age and smoking. In all TPOAb (-) patients, median (p2·5-p.97·5) TSH was 1·96 mIU/l (0·11-5·96 mIU/l) and median (p2·5-p.97·5) free T4 was 14·54 pmol/l (11·1 - 19·02 pmol/l). Applying these reference limits, we found a prevalence of overt and subclinical hypothyroidism of 0·9% and 3·05% respectively.

CONCLUSIONS

TSH distributes at higher values and free T4 at lower values in obese pregnant women compared to normal weight pregnant women. Thyroid hormone reference ranges derived from Chilean patients with negative TPOAb are different from the fixed internationally proposed reference ranges and may be used in the Hispanic population.

[Frequency of subclinical thyroid problems among women during the first trimester of pregnancy]

BACKGROUND

Thyroid hormones play an important role in fetal neural and cognitive development. Therefore thyroid abnormalities should be detected and treated early during pregnancy.

AIM

To assess the frequency and risk factors for functional thyroid disorders during the first trimester of pregnancy.

MATERIAL AND METHODS

A blood sample was obtained from women during their first trimester of pregnancy, consulting in a prenatal care facility. Women with known thyroid diseases were excluded from the study. Thyroid stimulating hormone (TSH), total thyroxine (T4) and free thyroxine (fT4) were measured by electrochemoluminiscence. Antithyroid peroxidase antibodies (anti TPO) were measured by enzyme immunoassay.

RESULTS

Five hundred and ten women aged 25.7 ± 6.6 years were assessed. The frequency of clinical hypothyroidism was 0.6%, subclinical hypothyroidism 35.3% and clinical hyperthyroidism 1%. Five percent of women with hypothyroidism and 3.5% of euthyroid women had positive anti TPO antibodies. There was no association between the frequency of thyroid diseases and risk factors for thyroid diseases.

CONCLUSIONS

There is a high frequency of subclinical thyroid diseases among women consulting in this prenatal care clinic.

Follow-up strategies for women treated for early breast cancer

BACKGROUND

Follow-up examinations are commonly performed after primary treatment for women with breast cancer. They are used to detect recurrences at an early (asymptomatic) stage.

OBJECTIVES

To assess the effectiveness of different policies of follow-up for distant metastases on mortality, morbidity and quality of life in women treated for stage I, II or III breast cancer.

SEARCH STRATEGY

We searched, the Breast Cancer Group's specialized register (May 14, 2004), the Cochrane Controlled Trial Register (Cochrane Library Issue 1, 2004), Medline (January 1966 - May 2004) and EMBASE (1988 - May 2004). References from retrieved articles were also checked.

SELECTION CRITERIA

All randomised controlled trials (RCTs) assessing the effectiveness of different policies of follow-up after primary treatment were reviewed for inclusion.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and eligibility for inclusion in the review. Data were pooled in an individual patient data meta-analysis for the two RCTs testing the effectiveness of different follow-up schemes. Subgroup analyses were conducted by age, tumour size and lymph node status.

MAIN RESULTS

Four RCTs involving 3055 women with breast cancer (clinical stage I, II or III) were included. Two of these involving 2563 women compared follow-up based on clinical visits and mammography with a more intensive scheme including radiological and laboratory tests. After pooling the data, no significant differences in overall survival (hazard ratio 0.96, 95% confidence interval 0.80 to 1.15) or disease-free survival (hazard ratio 0.84, 95% confidence interval 0.71 to 1.00) emerged. No differences in overall survival and disease-free survival emerged in subgroup analyses according to patient age, tumour size and lymph node status before primary treatment. In 1999, 10-year follow-up data became available for Rosselli Del Turco and no significant differences in overall survival were found. One RCT (296 women) compared follow-up performed by a hospital-based specialist to follow-up performed by general practitioners. No significant differences in time to detection of recurrence and quality of life emerged. Patient satisfaction was greater among patients treated by general practitioners. One RCT (196 women) compared regularly scheduled follow-up visits to less frequent visits restricted to the time of mammography. No significant differences emerged in interim use of telephone and frequency of GP's consultations.

AUTHORS' CONCLUSIONS

This updated review of RCTs conducted almost 20 years ago suggest that follow-up programs based on regular physical examinations and yearly mammography alone are as effective as more intensive approaches based on regular performance of laboratory and instrumental tests in terms of timeliness of recurrence detection, overall survival and quality of life. In one RCT, follow-up care performed by trained general practitioners working in an organized practice setting had comparable effectiveness to that delivered by hospital-based specialists in terms of quality of life and time to detection of distant metastases.

Follow-up strategies for women treated for early breast cancer

BACKGROUND

Follow-up examinations are commonly performed after primary treatment for women with breast cancer. They are used to detect recurrences at an early (asymptomatic) stage.

OBJECTIVES

To assess the effectiveness of different policies of follow-up for distant metastases on mortality, morbidity and quality of life in women treated for early breast cancer.

SEARCH STRATEGY

We searched the Breast Cancer Groups specialised register, the Cochrane Controlled Trials Register ( Cochrane Library Issue 4, 1999), MEDLINE (January 1975-September 1999) and EMBASE (1988-September 1999) using "Breast Neoplasms" and "follow-up". References from retrieved articles were also checked, as were the lists of presentations from recent breast cancer meetings.

SELECTION CRITERIA

All randomised controlled trials (RCTs) assessing the effectiveness of different policies of follow-up after primary treatment were reviewed for inclusion.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and eligibility for inclusion in the review. Data were pooled in an individual patient data meta-analysis for the two RCTs testing the effectiveness of different follow-up schemes. Subgroup analyses by age, tumour size and lymph node status before primary treatment are also presented.

MAIN RESULTS

Four RCTs involving 3204 women with early breast cancer (clinical stage I, II or III) have been included. Two RCTs involving 2563 women compared follow-up based on clinical visits and mammography with a more intensive scheme including radiological and laboratory tests. After pooling the data, no significant differences in overall survival (hazard ratio 0.96, 95% confidence interval 0.80 to 1.15) or disease-free survival (hazard ratio 0.84, 95% confidence interval 0.71 to 1.00) emerged. No differences in overall survival and disease-free survival emerged in subgroup analyses according to patient age, tumour size and lymph node status before primary treatment. One RCT (296 women) compared follow-up performed by a hospital-based specialist to follow-up performed by general practitioners. No significant differences in time to detection of recurrence and quality of life emerged. One RCT (196 women) compared regularly scheduled follow-up visits to less frequent visits restricted to the time of mammography. No significant differences emerged in interim use of telephone and frequency of GP's consultations.

REVIEWER'S CONCLUSIONS

Follow-up programs based on regular physical examinations and yearly mammography alone appear to be as effective as more intensive approaches based on regular performance of laboratory and instrumental tests in terms of timeliness of recurrence detection, overall survival and quality of life. In one RCT, follow up care performed by general practitioners had comparable effectiveness to that delivered by hospital based specialists in terms of quality of life and time to detection of distant metastases.