Levothyroxine dose adjustment in hypothyroid women achieving pregnancy through IVF

ObjectiveAbout one out of two women with primary hypothyroidism has to increase the dosage of exogenous levothyroxine (l-T4) during pregnancy. Considering the detrimental impact of IVF on thyroid function, it has been claimed but not demonstrated thatl-T4dose adjustment may be more significant in hypothyroid women who become pregnant after IVF.DesignRetrospective cohort study.MethodsHypothyroid-treated women who achieved a live birth through IVF were reviewed. Women could be included if thyroid function was well compensated withl-T4before the IVF cycle (i.e., serum TSH <2.5 mIU/l and serum free T4within the normal range). Serum TSH and dose adjustment were evaluated at five time points during pregnancy. The trimester ranges for serum TSH considered as reference to adjustl-T4therapy were 0.1–2.5 mIU/l for the first trimester, 0.2–3.0 mIU/l for the second trimester, and 0.3–3.0 mIU/l for the third trimester.ResultsThirty-eight women were selected. During the whole pregnancy 32 women (84%; 95% CI: 72–96%) required an increase in the dose ofl-T4. In most cases (n=28), this occured within the first 5–7 weeks of gestation (74%, 95% CI: 58–85%). At 5–7 weeks of gestation, the median (interquartile range) increase ofl-T4dose for the whole cohort was 26% (0–50%). At 30–32 weeks, it was 33% (14–68%). In order to identify predictive factors of dose adjustment, we compared women who did (n=28) and did not (n=10) adjustl-T4dosage at 5–7 weeks' gestation. Significant differences emerged for thyroid autoimmunity prevalence and for the distribution of hypothyroidism aetiology.ConclusionsThe vast majority of hypothyroid-treated women who achieve pregnancy through IVF need an increase in thel-T4dose during gestation. This requirement tends to occur very early during gestation.

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Gestation specific reference intervals for thyroid function tests in pregnancy

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm-2015-0569 ◽

2016 ◽

Vol 54 (8) ◽

Cited By ~ 6

Author(s):

Süleyman Akarsu ◽

Filiz Akbiyik ◽

Eda Karaismailoglu ◽

Zeliha Gunnur Dikmen

Keyword(s):

Pregnant Women ◽

Thyroid Function ◽

First Trimester ◽

Reference Intervals ◽

Specific Reference ◽

Thyroid Function Tests ◽

Second Trimester ◽

Third Trimester ◽

The Third ◽

Function Tests

AbstractThyroid function tests are frequently assessed during pregnancy to evaluate thyroid dysfunction or to monitor pre-existing thyroid disease. However, using non-pregnant reference intervals can lead to misclassification. International guidelines recommended that institutions should calculate their own pregnancy-specific reference intervals for free thyroxine (FT4), free triiodothyronine (FT3) and thyroid-stimulating hormone (TSH). The objective of this study is to establish gestation-specific reference intervals (GRIs) for thyroid function tests in pregnant Turkish women and to compare these with the age-matched non-pregnant women.Serum samples were collected from 220 non-pregnant women (age: 18–48), and 2460 pregnant women (age: 18–45) with 945 (39%) in the first trimester, 1120 (45%) in the second trimester, and 395 (16%) in the third trimester. TSH, FT4 and FT3 were measured using the Abbott Architect i2000SR analyzer.GRIs of TSH, FT4 and FT3 for first trimester pregnancies were 0.49–2.33 mIU/L, 10.30–18.11 pmol/L and 3.80–5.81 pmol/L, respectively. GRIs for second trimester pregnancies were 0.51–3.44 mIU/L, 10.30–18.15 pmol/L and 3.69–5.90 pmol/L. GRIs for third trimester pregnancies were 0.58–4.31 mIU/L, 10.30–17.89 pmol/L and 3.67–5.81 pmol/L. GRIs for TSH, FT4 and FT3 were different from non-pregnant normal reference intervals.TSH levels showed an increasing trend from the first trimester to the third trimester, whereas both FT4 and FT3 levels were uniform throughout gestation. GRIs may help in the diagnosis and appropriate management of thyroid dysfunction during pregnancy which will prevent both maternal and fetal complications.

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Pregnancy outcomes are not altered by variation in thyroid function within the normal range in women free of thyroid disease

Acta Endocrinologica ◽

10.1530/eje-17-0628 ◽

2018 ◽

Vol 178 (2) ◽

pp. 189-197 ◽

Cited By ~ 6

Author(s):

Flora Veltri ◽

Pierre Kleynen ◽

Lidia Grabczan ◽

Alexandra Salajan ◽

Serge Rozenberg ◽

...

Keyword(s):

Pregnant Women ◽

Thyroid Function ◽

Pregnancy Outcomes ◽

Thyroid Disease ◽

Thyroid Autoimmunity ◽

Thyroid Peroxidase ◽

Normal Range ◽

Baseline Characteristics ◽

Serum Tsh ◽

Tsh Levels

ObjectiveIn the recently revised guidelines on the management of thyroid dysfunction during pregnancy, treatment with thyroid hormone (LT4) is not recommended in women without thyroid autoimmunity (TAI) and TSH levels in the range 2.5–4.0 mIU/L, and in a recent study in that particular group of pregnant women, more complications were observed when a treatment with LT4 was given. The objective of the study was therefore to investigate whether variation in thyroid function within the normal (non-pregnant) range in women free of thyroid disease was associated with altered pregnancy outcomes?DesignCross-sectional data analysis of 1321 pregnant women nested within an ongoing prospective collection of pregnant women’s data in a single centre in Brussels, Belgium.MethodsThyroid peroxidase antibodies (TPO-abs), thyroid-stimulating hormone (TSH), free T4 (FT4) and ferritin levels were measured and baseline characteristics were recorded. Women taking LT4, with TAI and thyroid function outside the normal non-pregnant range were excluded. Pregnancy outcomes and baseline characteristics were correlated with all TSH and FT4 levels within the normal range and compared between two groups (TSH cut-off < and ≥2.5 mIU/L).ResultsTobacco use was associated with higher serum TSH levels (OR: 1.38; CI 95%: 1.08–1.74);P = 0.009. FT4 levels were inversely correlated with age and BMI (rho = −0.096 and −0.089;P < 0.001 and 0.001 respectively) and positively correlated with ferritin levels (rho = 0.097;P < 0.001). Postpartum haemorrhage (>500 mL) was inversely associated with serum FT4 levels (OR: 0.35; CI 95%: 0.13–0.96);P = 0.040. Also 10% of women free of thyroid disease had serum TSH levels ≥2.5 mIU/L.ConclusionsVariation in thyroid function during the first trimester within the normal (non-pregnant) range in women free of thyroid disease was not associated with altered pregnancy outcomes. These results add evidence to the recommendation against LT4 treatment in pregnant women with high normal TSH levels and without TPO antibodies.

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Relationship of Trimester-Specific Maternal Thyroid Function With Gestational Weight Gain And Birth Weight In Pregnant Women With Normal Thyroid Autoimmunity

10.21203/rs.3.rs-778871/v1 ◽

2021 ◽

Author(s):

Xin He ◽

Zhengyuan Wang ◽

Zehuan Shi ◽

Ping Liao ◽

Qin Yan ◽

...

Keyword(s):

Weight Gain ◽

Birth Weight ◽

Gestational Weight Gain ◽

Thyroid Function ◽

Thyroid Autoimmunity ◽

Second Trimester ◽

Z Score ◽

Third Trimester ◽

Normal Thyroid ◽

Gestational Weight

Abstract Background: Gestational weight gain (GWG) and birth weight are important indicators of maternal and infant health outcomes. Thyroid function may affect body composition and fetal growth during pregnancy. So far, on the premise of excluding thyroid autoimmunity interference, the correlation of thyroid function in different pregnancy with neonatal birth weight and maternal weight gain is still controversial. Methods: This study used data from a prospective birth cohort in Shanghai, China. Serum concentration of TSH, total thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3), free triiodothyronine (FT3), thyroglobulin antibody (TGAb), thyroid peroxidase antibody (TPOAb) were determined using chemiluminescence assay. Maternal GWG and neonatal sex-specific birth weight-for-gestational age Z-score was calculated.Results: Subjects with a higher BMI before pregnancy turned to have a lower GWG and an infant with a higher birth weight. GWG was negatively associated with maternal FT4 at the first and third trimester (p<0.05), and TT4 at the third trimester (p<0.05). GWG was positively associated with maternal FT3 at the second trimester (p<0.05). Lower birth weight Z-score were associated with higher FT4 at the second and third trimester (p<0.05), and higher TT4 at the second trimester (p<0.05). Conclusions: In the general pregnant population with normal thyroid autoimmunity, higher maternal FT4 and TT4 and lower FT3 are associated with less GWG. Higher maternal FT4 and TT4 have an infant with lower birth weight.

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Cigarette Smoking during Pregnancy Is Associated with Alterations in Maternal and Fetal Thyroid Function

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2008-0380 ◽

2009 ◽

Vol 94 (2) ◽

pp. 570-574 ◽

Cited By ~ 46

Author(s):

Beverley Shields ◽

Anita Hill ◽

Mary Bilous ◽

Beatrice Knight ◽

Andrew T. Hattersley ◽

...

Keyword(s):

Cigarette Smoking ◽

Pregnant Women ◽

Thyroid Function ◽

First Trimester ◽

Third Trimester ◽

Cord Serum ◽

Median Serum ◽

Fetal Thyroid ◽

The Relationship ◽

Serum Tsh

Abstract Context: Studies in the general population have shown lower serum TSH levels in smokers as compared with nonsmokers. Aim: Our aim was to examine whether smoking is associated with changes in thyroid function of pregnant women and their fetus. Subjects and Methods: We examined the relationship between smoking and thyroid function (serum TSH, free T4, and free T3) in two independent cohorts of pregnant women without a history of thyroid disorder or an overt biochemical thyroid dysfunction: 1) first-trimester cohort (median gestation 9 wk) (n = 1428) and 2) third-trimester cohort (gestation 28 wk) (n = 927). We also analyzed the relationship between maternal smoking and thyroid hormone levels in cord serum of 618 full-term babies born to the women in the third-trimester cohort. Results: In smokers compared with nonsmokers, median serum TSH was lower (first-trimester cohort: 1.02 vs. 1.17 mIU/liter, P = 0.001; third-trimester cohort: 1.72 vs. 1.90 mIU/liter, P = 0.037), and median serum FT3 was higher (first-trimester cohort: 5.1 vs. 4.9 pmol/liter, P < 0.0001; third-trimester cohort: 4.4 vs. 4.1 pmol/liter, P < 0.0001). In both cohorts, serum FT4 in smokers and nonsmokers were similar. The prevalence of anti-thyroperoxidase antibodies was also similar in smokers and nonsmokers in both cohorts. Cord serum TSH of babies born to smokers was lower than of those born to nonsmokers (6.7 vs. 8.1 mIU/liter, P = 0.009). Conclusions: Cigarette smoking is associated with changes in maternal thyroid function throughout the pregnancy and in fetal thyroid function as measured in cord blood samples.

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Infliximab clearance decreases in the second and third trimesters of pregnancy in inflammatory bowel disease

United European Gastroenterology Journal ◽

10.1177/2050640620964619 ◽

2020 ◽

pp. 205064062096461

Author(s):

Ana-Marija Grišić ◽

Maria Dorn-Rasmussen ◽

Bella Ungar ◽

Jørn Brynskov ◽

Johan F K F Ilvemark ◽

...

Keyword(s):

Inflammatory Bowel Disease ◽

Bowel Disease ◽

First Trimester ◽

Interquartile Range ◽

Therapeutic Drug ◽

Population Pharmacokinetic ◽

Second Trimester ◽

Third Trimester ◽

The Third ◽

Inflammatory Bowel

Background Infliximab therapy during pregnancy in inflammatory bowel disease is challenged by a dilemma between maintaining adequate maternal disease control while minimizing fetal infliximab exposure. We investigated the effects of pregnancy on infliximab pharmacokinetics. Methods The study population comprised 23 retrospectively identified pregnancies. Patients with inflammatory bowel disease were generally in clinical remission at pregnancy conception (74%) and received steady infliximab maintenance therapy (5 mg/kg q8w n = 17; q6w n = 4; q10w n = 1; 10 mg/kg q8w n = 1). Trough blood samples had been obtained in the same patients prior to pregnancy ( n = 119), the first trimester ( n = 16), second trimester ( n = 18), third trimester ( n = 7), and post-pregnancy ( n = 12). Data were analyzed using nonlinear mixed-effects population pharmacokinetic modelling. Results Dose-normalized infliximab concentrations were significantly higher during the second trimester (median 15 µg/mL/kg, interquartile range 10–21) compared to pre-pregnancy (7, 2–12; p = 0.003), the first trimester (9, 1–12; p = 0.04), or post-pregnancy (6, interquartile range 3–11; p > 0.05) in patients with inflammatory bowel disease. Similar trends were observed in the third trimester (13, 7–36; p > 0.05). A one-compartment model with linear elimination described the pharmacokinetics of infliximab (volume of distribution = 18.2 L; clearance 0.61 L/day). Maternal infliximab exposure was influenced by the second and third trimester of pregnancy and anti-infliximab antibodies, and not by pregnancy-imposed physiological changes in, for example, body weight or albumin. Infliximab clearance decreased significantly during the second and third trimesters by up to 15% as compared to pre- and post-pregnancy and the first trimester. The increased maternal infliximab exposure was weakly associated with lowered clinical disease activity. Pharmacokinetic model simulations of virtual patients indicated the increased maternal infliximab trough concentrations imposed by pregnancy will not completely counteract the decrease in infliximab concentration if therapy is paused in the third trimester. Conclusion Infliximab clearance decreases significantly in the second and third trimesters, leading to increasing maternal infliximab concentrations in any given regimen. Maternal infliximab levels may thus be maintained as constant in a de-intensified regimen by therapeutic drug monitoring guidance in inflammatory bowel disease.

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The Effect of Preserving Pregnancy in Cervical Cancer Diagnosed During Pregnancy: A Retrospective Study

10.21203/rs.3.rs-507502/v1 ◽

2021 ◽

Author(s):

Zuoxi He ◽

Chuan Xie ◽

Xiaorong Qi ◽

Zhengjun Hu ◽

Yuedong He

Keyword(s):

Cervical Cancer ◽

Rare Event ◽

Oncologic Outcome ◽

First Trimester ◽

Second Trimester ◽

Third Trimester ◽

Delayed Treatment ◽

The Third ◽

Survival Difference ◽

Estimated Blood Loss

Abstract ObjectiveCervical cancer diagnosed during pregnancy is a rare event, and data regarding efficacy of cancer treatment during pregnancy is limited. This study aimed to assess the safety of continuation of the pregnancy for mother and fetus when concomitantly diagnosed with cervical cancer.MethodsThis study retrospectively analyzed all cervical cancer patients diagnosed while pregnant or immediately postpartum, inclusive from Jan 2010 to June 2019 at our institute. Patient clinical details and follow-up were obtained from hospital records. ResultsThe study comprised 40 patients with clinical cancer stages of ⅠA1 (1/40, 2.5%); ⅠB1 (15/40, 37.5%); IB2 (10/40, 25%); ⅡA (12/40, 30%); and ⅡB (2/40, 5%). There were 38 patients diagnosed during pregnancy, and 2 diagnosed in the postpartum period. Of the 38 patients, 17 were diagnosed in the first trimester, 13 in the second trimester, and 8 in the third trimester. Ten of 38 patients (26.3%) continued their pregnancy after learning of their diagnosis; 7 (70%) in the third trimester and 3 (30%) in the second trimester. The mean time from diagnosis to surgery in the patients who continued their pregnancy was 52.7 days, which was statistically significantly greater than the termination of pregnancy group (52.7 vs 16.3 days, P < 0.01). Notably, there was no survival difference between the 2 groups (100% vs 90.91%, P =0.54), and none of the pregnant women who ultimately died had delayed treatment due to pregnancy. Similarly, the surgical estimated blood loss and operative duration comparing the 2 groups were not significantly different. ConclusionsIn the present study, the gestational age of pregnancy at the time of initial diagnosis of cervical cancer was an important determinant in the disease management. Continuation of the pregnancy when diagnosed with cervical cancer did not affect the oncologic outcome of the mother nor increase either surgical or obstetric complications. Additionally, the use of neoadjuvant chemotherapy did not threaten the health of the fetus. These results may be useful in counseling patients facing the diagnosis of cervical cancer during pregnancy.

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Spiral artery blood flow during pregnancy: a systematic review and meta-analysis.

10.21203/rs.2.16611/v2 ◽

2019 ◽

Author(s):

Veronique Schiffer ◽

Laura Evers ◽

Sander de Haas ◽

Chahinda Ghossein ◽

Salwan Al-Nasiry ◽

...

Keyword(s):

Systematic Review ◽

Blood Flow ◽

Meta Analysis ◽

Resistance Index ◽

First Trimester ◽

Trophoblast Invasion ◽

Cochrane Library ◽

Second Trimester ◽

Spiral Artery ◽

Third Trimester

Abstract Background: Downstream remodeling of the spiral arteries (SpA) decreases utero-placental resistance drastically, allowing sustained and increased blood flow to the placenta at all circumstances. We systematically evaluated available reports to visualize adaptation of spiral arteries throughout pregnancy by ultra-sonographic measurements and evaluated when this process is completed.Methods: A systematic review and meta-analysis of spiral artery flow (pulsatility index (PI), resistance index (RI) and peak systolic velocity (PSV)) was performed. English articles were obtained from Pubmed, EMBASE and Cochrane Library and included articles were assessed on quality and risk of bias. Weighted means of Doppler indices were calculated using a random-effects model. Results: In healthy pregnancies, PI and RI decreased from 0.75 (95% CI: 0.67-0.83) and 0.49 (95% CI: 0.46-0.53) in the first trimester to 0.52 (95% CI: 0.48-0.56, p=0.003) and 0.40 (95% CI: 0.38-0.42, p=0.080) in the second trimester and to 0.49 (95% CI: 0.44-0.53, p=0.510) and 0.36 (95% CI: 0.35-0.37, p=0.307) in the third trimester, respectively. In parallel, PSV altered from 0.24 m/s (95% CI: 0.17-0.31 m/s) to 0.28 m/s (95% CI: 0.22-0.34 m/s, p=0.377) and to 0.25 m/s (95% CI: 0.21-0.28 m/s, p=0.919) in the three trimesters. In absence of second and third trimester Doppler data in complicated gestation, only a difference in PI was observed between complicated and healthy pregnancies during the first trimester (1.49 vs 0.76, p<0.001). Although individual studies have identified differences in PI between SpA located in the central part of the placental bed versus those located at its periphery, this meta-analysis could not confirm this (p=0.349).Conclusions: This review and meta-analysis concludes that an observed decrease of SpA PI and RI from the first towards the second trimester parallels the physiological trophoblast invasion converting SpA during early gestation, a process completed in the midst of the second trimester. Higher PI and RI were found in SpA of complicated pregnancies compared to healthy pregnancies, possibly reflecting suboptimal utero-placental circulation. Longitudinal studies examining comprehensively the predictive value of spiral artery Doppler for complicated pregnancies are yet to be carried out.

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Vitamin D status in pregnant Indian women across trimesters and different seasons and its correlation with neonatal serum 25-hydroxyvitamin D levels

British Journal Of Nutrition ◽

10.1017/s000711451100170x ◽

2011 ◽

Vol 106 (9) ◽

pp. 1383-1389 ◽

Cited By ~ 64

Author(s):

R. K. Marwaha ◽

N. Tandon ◽

S. Chopra ◽

N. Agarwal ◽

M. K. Garg ◽

...

Keyword(s):

Vitamin D ◽

Hypovitaminosis D ◽

First Trimester ◽

Strong Positive Correlation ◽

Vitamin D Status ◽

Second Trimester ◽

Third Trimester ◽

Indian Women ◽

Hydroxyvitamin D ◽

25 Hydroxyvitamin D

The present cross-sectional study was conducted to determine the vitamin D status of pregnant Indian women and their breast-fed infants. Subjects were recruited from the Department of Obstetrics, Armed Forces Clinic and Army Hospital (Research and Referral), Delhi. A total of 541 apparently healthy women with uncomplicated, single, intra-uterine gestation reporting in any trimester were consecutively recruited. Of these 541 women, 299 (first trimester, ninety-seven; second trimester, 125; third trimester, seventy-seven) were recruited in summer (April–October) and 242 (first trimester, fifty-nine, second trimester, ninety-three; third trimester, ninety) were recruited in winter (November–March) to study seasonal variations in vitamin D status. Clinical, dietary, biochemical and hormonal evaluations for the Ca–vitamin D–parathormone axis were performed. A subset of 342 mother–infant pairs was re-evaluated 6 weeks postpartum. Mean serum 25-hydroxyvitamin D (25(OH)D) of pregnant women was 23·2 (sd 12·2) nmol/l. Hypovitaminosis D (25(OH)D < 50 nmol/l) was observed in 96·3 % of the subjects. Serum 25(OH)D levels were significantly lower in winter in the second and third trimesters, while serum intact parathormone (iPTH) and alkaline phosphatase levels were significantly higher in winter in all three trimesters. A significant negative correlation was found between serum 25(OH)D and iPTH in mothers (r − 0·367, P = 0·0001) and infants (r − 0·56, P = 0·0001). A strong positive correlation was observed between 25(OH)D levels of mother–infant pairs (r 0·779, P = 0·0001). A high prevalence of hypovitaminosis D was observed in pregnancy, lactation and infancy with no significant inter-trimester differences in serum 25(OH)D levels.

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Histogenesis and Histomorphometric study of Human Fetal Small Intestine

Ethiopian Journal of Health Sciences ◽

10.4314/ejhs.v29i6.5 ◽

1970 ◽

Vol 29 (6) ◽

Author(s):

Salva MN ◽

Chandni Gupta ◽

Arvind Kumar Pandey ◽

Nitesh Kumar ◽

Sushma R Kotian ◽

...

Keyword(s):

Small Intestine ◽

Normal Growth ◽

Later Life ◽

First Trimester ◽

Second Trimester ◽

Third Trimester ◽

Histomorphometric Study ◽

Microscopic Features ◽

Early Life Events ◽

Muscularis Externa

Background: Intestine plays a major role for the normal growth of the fetus during the prenatal period. The process of the embryonic development is not quantified histologically. Therefore the main aim of the study was to measure the thickness of all part of the wall of the small intestine that are mucosa, submucosa and muscularis externa and to look for the appearance of the Brunner’s glands and Peyer’s patches in the submucosa of duodenum and ileum.Methods: The present study was carried out on 30 fetuses of gestational ages ranging from 11-36 weeks. Ten fetuses from each trimester were used in the study. Fetal small intestine were dissected carefully, and were separated as duodenum, jejunum & ileum and fixed in formalin solution. The tissue was processed for histology and then slides were stained with Haematoxylin and Eosin. The microscopic features were noted using light microscope.Results: The thickness of the mucosa, submucosa and the muscularis externa was observed to be increased in first trimester, decreased in the second trimester and again increased in the third trimester, which could be because of the increase cell turnover and the arrangement of the collagen fibers as to support the mucosa and the muscularis externa.Conclusion: Thus, the knowledge of the histogenesis and histomorphometry of the human fetal small intestine is crucial for the adult gastroenterologist to appreciate, because of the potential for these early life events to affect the responsiveness of the intestine to physiological or pathological challenges in later life.

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Thyroid function in children and adolescents with Hashimoto's thyroiditis after l-thyroxine discontinuation

Endocrine Connections ◽

10.1530/ec-17-0023 ◽

2017 ◽

Vol 6 (4) ◽

pp. 206-212 ◽

Cited By ~ 7

Author(s):

Giorgio Radetti ◽

Mariacarolina Salerno ◽

Chiara Guzzetti ◽

Marco Cappa ◽

Andrea Corrias ◽

...

Keyword(s):

Children And Adolescents ◽

Thyroid Function ◽

Hashimoto’S Thyroiditis ◽

Outcome Measure ◽

Hashimoto's Thyroiditis ◽

Pediatric Endocrinology ◽

Normal Range ◽

Discontinuation Of Treatment ◽

One Year ◽

Serum Tsh

Objective Thyroid function may recover in patients with Hashimoto’s thyroiditis (HT). Design To investigate thyroid function and the need to resume l-thyroxine treatment after its discontinuation. Setting Nine Italian pediatric endocrinology centers. Patients 148 children and adolescents (25 m and 123 f) with HT on treatment with l-thyroxine for at least one year. Intervention and main outcome measure Treatment was discontinued in all patients, and serum TSH and fT4 concentrations were measured at the time of treatment discontinuation and then after 2, 6, 12 and 24 months. Therapy with l-thyroxine was re-instituted when TSH rose >10 U/L and/or fT4 was below the normal range. The patients were followed up when TSH concentrations were between 5 and 10 U/L and fT4 was in the normal range. Results At baseline, TSH was in the normal range in 139 patients, and was between 5 and 10 U/L in 9 patients. Treatment was re-instituted after 2 months in 37 (25.5%) patients, after 6 months in 13 patients (6.99%), after 12 months in 12 patients (8.6%), and after 24 months in an additional 3 patients (3.1%). At 24 months, 34 patients (34.3%) still required no treatment. TSH concentration >10 U/L at the time of diagnosis was the only predictive factor for the deterioration of thyroid function after l-thyroxine discontinuation. Conclusions This study confirms that not all children with HT need life-long therapy with l-thyroxine, and the discontinuation of treatment in patients with a TSH level <10 U/L at the time of diagnosis should be considered.

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