Subclinical hypothyroidism in children: normal variation or sign of a failing thyroid gland?

Severe Phenotype of Non-alcoholic Fatty Liver Disease in Pediatric Patients with Subclinical Hypothyroidism: a Retrospective Multicenter Study from Korea

BACKGROUND

It is uncertain whether non-alcoholic fatty liver disease (NAFLD) is associated with subclinical hypothyroidism (SH) in pediatric patients. The purpose of this study was to investigated the prevalence and related factors of SH in pediatric patients with NAFLD. We also evaluate the association between liver fibrosis and SH.

METHODS

We retrospectively reviewed medical records for patients aged 4 to 18 years who were diagnosed with NAFLD and tested for thyroid function from January 2015 to December 2019 at 10 hospitals in Korea.

RESULTS

The study included 428 patients with NAFLD. The prevalence of SH in pediatric NAFLD patients was 13.6%. In multivariate logistic regression, higher levels of steatosis on ultrasound and higher aspartate aminotransferase to platelet count ratio index (APRI) score were associated with increased risk of SH. Using receiver operating characteristic curves, the optimal cutoff value of the APRI score for predicting SH was 0.6012 (area under the curve, 0.67; P < 0.001; sensitivity 72.4%, specificity 61.9%, positive predictive value 23%, and negative predictive value 93.5%).

CONCLUSION

SH was often observed in patients with NAFLD, more frequently in patients with more severe liver damage. Thyroid function tests should be performed on pediatric NAFLD patients, especially those with higher grades of liver steatosis and fibrosis.

Thyroid hormone therapy in congenital hypothyroidism and pediatric hypothyroidism

The evaluation and management of hypothyroidism in children are similar to adults, but there are important differences based on the dependence on normal thyroid function for neurocognitive and physical development. In the pediatric population, hypothyroidism is frequently categorized as congenital or acquired hypothyroidism, depending on the age of presentation and the underlying etiology. The evaluation and management of children and adolescents with hypothyroidism are determined by the etiology as well as by the age at diagnosis, severity of the hypothyroidism, and the response to thyroid hormone replacement therapy. Children and adolescents require higher weight-based doses for thyroid hormone replacement than do adults, likely due to a shorter half-life of thyroxine (T4) and triiodothyronine (T3) in children, but weight-based dose requirements decrease as the child advances into adulthood. Multiple gaps in knowledge remains regarding how to optimize the treatment of hypothyroidism in pediatric patients, including (but not limited to) the selection of patients with subclinical hypothyroidism for treatment, and the potential benefit of combined LT3/LT4 therapy for patients with persistent symptoms and/or low T3 on LT4 monotherapy. The life-long impact on growth and development, and potentially on long-term cardiovascular and psychosocial health, are significant and highlight the importance of future prospective studies in pediatric patients to explore these areas of uncertainty.

Pesticide Exposure and Thyroid Function in Elementary School Children Living in an Agricultural Area, Brebes District, Indonesia

BACKGROUND

Children living in agricultural areas are at risk of exposure to pesticides due to their involvement in agricultural activities. Pesticides are one of the chemicals classified as endocrine disrupting chemicals.

OBJECTIVE

To examine the association between exposure to organophosphate pesticides and the occurrence of thyroid dysfunction in children.

METHODS

This cross-sectional study was conducted on 66 children in two elementary schools located in an agricultural area in Brebes District, Indonesia, in 2015. To determine the pesticide exposure history, we analyzed urine samples and completed a questionnaire. Meanwhile, thyroid function tests were performed.

RESULTS

Organophosphate pesticide metabolites were detected in urine samples of 15 (23%) of 66 children. Thyroid stimulating hormone (TSH) levels >4.5 μIU/mL were detected in 24 (36%) children. Free thyroxine (FT4) levels of all participants were normal. The mean TSH level in children with positive urinary organophosphate pesticide metabolites (7.74 μIU/ mL) was significantly (p=0.005) higher than that in those who were negative (4.34 μIU/mL). The prevalence of hypothyroidism in children with positive urinary organophosphate pesticide metabolites (67%) was significantly higher than that in those who were negative (27%; PR 2.4, 95% CI 1.4 to 4.3).

CONCLUSION

A history of pesticide exposure could be used as a risk factor for the occurrence of thyroid dysfunction in children living in agricultural areas.

Phthalates and thyroid function in preschool age children: Sex specific associations

BACKGROUND

Research relating either prenatal or concurrent measures of phthalate exposure to thyroid function in preschool children is inconclusive.

METHODS

In a study of inner-city mothers and their children, metabolites of di-n-butyl phthalate, butylbenzyl phthalate, di-isobutyl phthalate, di(2-ethylhexyl) phthalate, and diethyl phthalate were measured in a spot urine sample collected from women in late pregnancy and from their children at age 3years. We measured children's serum free thyroxine (FT4) and thyroid stimulating hormone (TSH) at age 3. Linear regression models were used to investigate the associations between phthalate metabolites, measured in maternal urine during late pregnancy and measured in child urine at age 3 and thyroid function measured at age 3.

RESULTS

Mean concentrations (ranges) were 1.42ng/dL (1.02-2.24) for FT4, and 2.62uIU/mL (0.61-11.67) for TSH. In the children at age 3, among girls, FT4 decreased with increasing log_e mono-n-butyl phthalate [estimated b=-0.06; 95% CI: (-0.09, -0.02)], log_e mono-isobutyl phthalate [b=-0.05; 95% CI: (-0.09, -0.01)], log_e monoethyl phthalate [b=-0.04; 95% CI: (-0.07, -0.01)], and log_e mono(2-ethyl-5-hydroxyhexyl) phthalate [b=-0.04; 95% CI: (-0.07, -0.003)] and log_e mono(2-ethyl-5-oxy-hexyl) phthalate [b=-0.04; 95% CI: (-0.07, -0.004)]. In contrast, among boys, we observed no associations between FT4 and child phthalate metabolites at age 3. On the other hand, in late gestation, FT4 increased with increasing log_e mono-(2-ethylhexyl) phthalate [estimated b=0.04; 95% CI: (0.02, 0.06)] and no sex difference was observed. We found no associations between phthalate biomarkers measured in either the child or prenatal samples and TSH at age 3.

CONCLUSIONS

The data show inverse and sex specific associations between specific phthalate metabolites measured in children at age 3 and thyroid function in preschool children. These results may provide evidence for the hypothesis that reductions in thyroid hormones mediate associations between early life phthalate exposure and child cognitive outcomes.

Persistent Organic Pollutants and the Association with Maternal and Infant Thyroid Homeostasis: A Multipollutant Assessment

BACKGROUND

Disruption of thyroid homeostasis has been indicated in human studies targeting effects of persistent organic pollutants (POPs). Influence on the maternal thyroid system by POPs is of special interest during pregnancy because such effects could impair infant thyroid homeostasis.

OBJECTIVES

We investigated the association between POPs and thyroid-stimulating hormone (TSH) and thyroid hormones (THs) in mother and child pairs from the Northern Norway Mother-and-Child Contaminant Cohort Study (MISA).

METHODS

Nineteen POPs and 10 thyroid parameters were analyzed in serum from 391 pregnant women in their second trimester. In addition, TSH concentrations in heel-prick samples from the infants were analyzed by the Norwegian Newborn Screening program. Association studies with a multipollutant approach were performed using multivariate analyses; partial least squares (PLS) regression, hierarchical clustering, and principal component analysis (PCA).

RESULTS

Several POPs were significantly associated with TSH and THs: a) PFOS was positively associated with TSH; b) PCBs, HCB, and nonachlors were inversely associated with T3, T4, and FT4; and, c) PFDA and PFUnDA were inversely associated with T3 and FT3. After mutual adjustments for the other contaminants, only PFDA and PFUnDA remained significantly associated with T3 and FT3, respectively. Infants born to mothers within the highest TSH quartile had 10% higher mean concentrations of TSH compared with children born to mothers in the lowest TSH quartile.

CONCLUSION

The present results suggest that background exposures to POPs can alter maternal thyroid homeostasis. This research contributes to the understanding of multipollutant exposures using multivariate statistical approaches and highlights the complexity of investigating environmental concentrations and mixtures in regard to maternal and infant thyroid function. Citation: Berg V, Nøst TH, Pettersen RD, Hansen S, Veyhe AS, Jorde R, Odland JØ, Sandanger TM. 2017. Persistent organic pollutants and the association with maternal and infant thyroid homeostasis: a multipollutant assessment. Environ Health Perspect 125:127-133; http://dx.doi.org/10.1289/EHP152.

Unfavorable Course of Subclinical Hypothyroidism in Children with Hashimoto's Thyroiditis Compared to Those with Isolated Non-Autoimmune Hyperthyrotropinemia

Subclinical hypothyroidism (SCH) is a common problem in pediatric population, and the natural history of SCH varies depending on its etiology. Whether Hashimoto's thyroiditis (HT) negatively affects the natural course of SCH was investigated in pediatric patients without concomitant diseases. Predictors for levothyroxine medication were also evaluated. Medical records of 109 children with SCH (91 girls, 5?18 years) diagnosed between 2005 and 2014 were retrospectively reviewed. Patients were classified into HT (n = 37) and isolated non-autoimmune hyperthyrotropinemia (iso-NAHT, n = 72). During median 2 years of follow-up, only 10.1% of SCH patients eventually initiated levothyroxine, and HT patients showed a higher probability of requiring levothyroxine medication than iso-NAHT patients (21.6% vs. 4.2%). Underlying HT independently predicted deterioration of thyroid function, leading to levothyroxine medication (hazard ratios [HRs], 4.6 vs. iso-NAHT, P = 0.025). High titers of anti-thyroglobulin antibodies (TGAbs) predicted later medication in the HT group (HRs, 28.2 vs. normal TGAbs, P = 0.013). Most pediatric SCH showed benign and self-remitting courses. Underlying HT significantly increases the risk for levothyroxine medication, especially with high titers of TGAbs.

Normative Thyroid-Stimulating Hormone Values for Healthy Nigerian Newborns

BACKGROUND

Congenital hypothyroidism is a common congenital endocrine disorder prevailing all over the world. No nationwide screening exists for any sub-Saharan country. We present normative cord and capillary thyroid-stimulating hormone (TSH) values for healthy Nigerian newborns.

SUBJECTS AND METHODS

A cross-sectional study was carried out in 6 university hospitals in Nigeria between January 1 and December 31, 2013. Cord and heel blood placed on 4 concentric circles on a Whartman filter paper were analysed for TSH within 1 week of collection using AutoDelfia 1235 immunoassay (Perkin Elmer Wallace, Boston, Mass., USA) at Charité - Universitätsmedizin Berlin, Berlin, Germany. The mean TSH levels of the newborns were determined, considering their sex, birthweight, socioeconomic status, and birth city. The association between the mean TSH level and other parameters was determined by analysis of variance.

RESULTS

A total of 2,014 subjects were recruited during the study period. The mean TSH value for the subjects was 1.86 μIU/ml, and 98.1% of the newborns were within the 2.5th and 97.5th percentiles (range: 0.09-7.90 μIU/ml) of the TSH levels. We collected 247 cord and 1,767 heel samples, respectively, and the range was slightly higher in samples from cord blood.

CONCLUSION

The study highlights the normal reference values for capillary/cord TSH levels in term Nigerian newborns. TSH was higher in one region, attributable to earlier sampling, but was not influenced by gender, socioeconomic status, or birthweight.

Prevalence and Determinants of True Thyroid Dysfunction Among Pediatric Referrals for Abnormal Thyroid Function Tests

Background/Aims. Abnormalities in thyroid function tests (TFTs) are a common referral reason for pediatric endocrine evaluation. However, a sizable proportion of these laboratory abnormalities do not warrant therapy or endocrine follow-up. The objectives of this study were (a) to evaluate the prevalence of true thyroid dysfunction among pediatric endocrinology referrals for abnormal TFTs; (b) to identify the historical, clinical, and laboratory characteristics that predict decision to treat. Methods. This was a retrospective chart review of patients evaluated in pediatric endocrinology office during a weekly clinic designated for new referrals for abnormal TFTs in 2010. Results. A total of 230 patients were included in the study. Median age at referral was 12 years (range = 2-18); 56% were females. Routine screening was cited as the reason for performing TFTs by 33% patients. Majority was evaluated for hypothyroidism (n = 206). Elevated thyroid-stimulating hormone was the most common referral reason (n = 140). A total of 41 out of 206 patients were treated for hypothyroidism. Conclusions. Prevalence of hypothyroidism was 20%. Thyroid follow-up was not recommended for nearly one third of the patients. Among all the factors analyzed, an elevated thyroid-stimulating hormone level and antithyroglobulin antibodies strongly correlated with the decision to treat (P < .005).

Triagem de hipotireoidismo em crianças - Visão dos médicos da atenção primária à saúde de um município de médio porte

Objetivo: Avaliar quais parâmetros os médicos da atenção primária à saúde do município de São Carlos, SP, Brasil, adotam para realizar triagem de função tireoidiana em crianças e adolescentes, quais exames complementares são solicitados e qual a conduta diante de resultados laboratoriais alterados. Métodos: Estudo transversal descritivo, no qual participaram 26 profissionais, correspondendo a 96,3% de todos os médicos da atenção primária da cidade que atuam no cuidado de crianças e adolescentes. Os participantes responderam por escrito quais as três situações mais frequentes na prática clínica em que indicavam triagem de hipotireoidismo na população pediátrica, quais os exames laboratoriais solicitados nesta avaliação e a qual conduta frente a exames com resultados alterados. Resultados: As situações clínicas mais frequentes apontadas pelos participantes como indicações de avaliação tireoidiana foram: obesidade, com 23 respostas (88,5%); baixa estatura, com 16 (61,5%); e síndrome de Down, com 8 (30,8%). Nove médicos (34,6%) responderam realizar o rastreio pela dosagem de TSH e T4l e outros 9 (34,6%), pela dosagem de TSH isolado. A conduta mais frequente diante de um resultado alterado foi o encaminhamento ao endocrinologista pediátrico, com 14 respostas (53,8%). Conclusão: O cenário encontrado neste estudo mostra que exames de função tireoidiana são solicitados rotineiramente por médicos da atenção primária no acompanhamento de crianças obesas. Como a obesidade infantil tem uma alta prevalência, isso pode determinar aumento importante dos custos do serviço de saúde e sobrecarga nos serviços de atenção especializada.

Evaluation of Subclinical Hypothyroidism in Children and Adolescents: A Single-Center Study

The main purpose of our retrospective study was to evaluate the medical care of the patients with subclinical hypothyroidism (sHT) and to investigate the rationale for administering L-thyroxine (LT-4) to young sHT patients. Patients and Methods. Based on a retrospective review of the charts of 261 patients referred to the Endocrinology Outpatient Clinic between 2009 and 2014 with suspicion of sHT, 55 patients were enrolled for further analysis. Data collected was baseline age, anthropometric measurements, serum TSH, fT4, fT3, anti-thyroid autoantibodies, positive family history, absence/presence of clinical symptoms, length of follow-up, and data concerning LT-4 therapy (therapy: T1; no therapy: T0). Results. T1 encompassed 33 (60.0%) patients. There were no differences between T1 and T0 (p > 0.05) with regard to age, TSH concentrations, BMI Z-score, and hSDS values, though follow-up was longer in T1 (p < 0.01). Four (11.8%) children in T1 and none in T0 had a positive family history of thyroid disorders. Fifteen (68.2%) patients in group T0 became euthyroid. One (1.8%) girl (T1) developed overt hypothyroidism. Conclusions. A small percentage of patients can proceed to overt hypothyroidism. Only positive family history seemed to influence the decision to initiate LT-4 therapy. Further prospective studies are warranted in order to establish treatment indications, if any, and the mean recommended dosage of LT-4.

Thyroid function and autoimmunity in children and adolescents with Type 1 Diabetes Mellitus

We evaluated 233 children and adolescents with T1 Diabetes to analyze the prevalence and characteristics of Autoimmune Thyroid Disease. AITD was found in 23%, the majority being female and patients older than 5 years of age. Screening is mandatory, and the best approach could be guided by gender and age.

Relationships between thyroid function and autoimmunity with metabolic derangement at the onset of type 1 diabetes: a cross-sectional and longitudinal study

BACKGROUND

Type 1 diabetes (T1DM) is an autoimmune disease often associated with thyroid abnormalities.

PURPOSE

We investigated the correlation between thyroid function and metabolic derangement at onset and the influence of autoimmunity on thyroid function at onset and subsequently.

METHODS

We evaluated 152 patients diagnosed with T1DM between 2000 and 2012 at onset and during a mean follow-up of 5.45 ± 2.8 years. Thyroid function at onset was correlated with metabolic derangement (degree of acidosis, metabolic control and adrenal function) and compared with that of 78 healthy children. Follow-up consisted of regular evaluation of thyroid function and autoimmunity.

RESULTS

Thyroid hormonal pattern was not influenced at onset by thyroid autoimmunity, but only by metabolic derangement: pH and base excess in fact were significantly lower in patients with impaired thyroid function (p < 0.0001). Patients presenting normal thyroid function at onset showed a reduced conversion from FT4 to FT3 compared to nondiabetic children (FT3/FT4 0.3 ± 0.4 in the control group, 0.24 ± 0.4 in diabetic patients, p < 0.0001). Multiple regression analysis showed the highest correlation (negative) between FT3 levels at onset and base excess (p < 0.005). Thyroid abnormalities related to metabolic derangement disappeared during follow-up. Patients with thyroid antibodies at T1DM onset were at higher risk to require levothyroxine treatment during follow-up (p < 0.05).

CONCLUSIONS

Thyroid function at T1DM onset is mainly influenced by metabolic derangement, irrespective of thyroid autoimmunity. Antithyroid antibodies evaluation at T1DM onset may be helpful to define which patients are at higher risk of developing hypothyroidism.

Subclinical hypothyroidism in children and adolescents: is it clinically relevant?

Although subclinical hypothyroidism (SH) is a common clinical problem, its diagnosis tends to be incidental. According to the definition, it should be asymptomatic, only detectable by screening. The presence or coincidence of any symptoms leads to L-thyroxine treatment. The clinical presentation, especially in younger patients with subclinical hypothyroidism, is still under dispute. Accordingly, the aim of this paper was to review the literature from the past seven years. The literature search identified 1,594 potentially relevant articles, of which 24 met the inclusion criteria. Few studies focus on the symptomatology of subclinical hypothyroidism, and most of them analyzed a small number of subjects. A significant correlation was found by some authors between subclinical hypothyroidism and a higher risk of hypertension, dyslipidemia, and migraine. No evidence of the impact of subclinical hypothyroidism on weight, growth velocity, and puberty was revealed. As the quality of most studies is poor and no definite conclusions can be drawn, randomized, large-scale studies in children and adolescents are warranted to determine the best care for patients with SH.

Prevalence of thyroid autoantibodies in children, adolescents and young adults with type 1 diabetes in Kuwait

OBJECTIVE

To investigate the prevalence of thyroid autoimmunity among children and adolescents with type 1 diabetes in Kuwait.

SUBJECTS AND METHODS

In a mixed cross-sectional and longitudinal study, anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-TG) were measured in 232 subjects (118 males and 114 females) with type 1 diabetes.

RESULTS

The mean age of the total study population was 10.9 ± 3.6 years (range 1-21), and the median diabetes duration was 3.9 years (range 0-16). At the initial screening, 57 out of 232 (24.6%) patients had positive antibodies, and of the remaining 175 patients, who were antibody negative,131 (74.3%) were followed up for 4-9 years. 23 out of these 131 (17.7%) patients became antibody positive, with a cumulative prevalence of elevated antibodies of 34.5%. Anti-TPO was present in 34 (14.7%), anti-TG in 23 (9.9%) and both antibodies in 23 (9.9%) patients. Thyroid antibodies presented early within the first 5 years of the onset of diabetes (63.2 vs. 36.8%, p < 0.05). The prevalence of elevated thyroid antibodies increased after the onset of puberty in both females and males (p < 0.0001). A total of 58.7% of the patients with positive antibodies were females compared to 41% males (p < 0.0001). The basal thyroid-stimulating hormone was higher in subjects with positive antibodies (5.1 ± 10.7 mIU/l) compared to those who were antibody negative (1.79 ± 0.87 mIU/l, p < 0.001). Furthermore, 30 out of 232 (12.9%) patients developed thyroid dysfunction.

CONCLUSION

In this study, a high prevalence of thyroid autoimmune antibodies was found in patients either at the onset of type 1 diabetes or within the 4-9 years of follow-up.

Medical and non-medical complications among children and adolescents with excessive body weight

BACKGROUND

The burden of disease from childhood obesity is considerable worldwide, as it is associated with several co-morbidities, such as dyslipidemia, hypertension, type 2 diabetes (T2DM), orthopedic and psychosocial problems. We aimed at determining the prevalence of these complications in a population of children and adolescents with body weight excess.

METHODS

This is a cohort study including 774 new patients (1.7 - 17.9 yrs, mean 11.1 ± 3.0) attending a pediatric obesity care center. We assessed personal and family medical histories, physical examination, systemic blood pressure, biochemical screening tests.

RESULTS

We found that the great majority of the children suffered from at least one medical complication. Orthopedic pathologies were the most frequent (54%), followed by metabolic (42%) and cardiovascular disturbances (31%). However, non-medical conditions related to well-being, such as bullying, psychological complaints, shortness of breath or abnormal sleeping patterns, were present in the vast majority of the children (79.4%). Family history of dyslipidemia tends to correlate with the child's lipids disturbance (p = .053), and ischemic events or T2DM were correlated with cardiovascular risk factors present in the child (p = .046; p = .038, respectively).

CONCLUSIONS

The vast majority of obese children suffer from medical and non-medical co-morbidities which must be actively screened. A positive family history for cardiovascular diseases or T2DM should be warning signs to perform further complementary tests. Furthermore, well-being related-complaints should not be underestimated as they were extremely frequent.

Measures of thyroid function among Belarusian children and adolescents exposed to iodine-131 from the accident at the Chernobyl nuclear plant

BACKGROUND

Thyroid dysfunction after exposure to low or moderate doses of radioactive iodine-131 (131I) at a young age is a public health concern. However, quantitative data are sparse concerning 131I-related risk of these common diseases.

OBJECTIVE

Our goal was to assess the prevalence of thyroid dysfunction in association with 131I exposure during childhood (≤ 18 years) due to fallout from the Chernobyl accident.

METHODS

We conducted a cross-sectional analysis of hypothyroidism, hyperthyroidism, autoimmune thyroiditis (AIT), serum concentrations of thyroid-stimulating hormone (TSH), and autoantibodies to thyroperoxidase (ATPO) in relation to measurement-based 131I dose estimates in a Belarusian cohort of 10,827 individuals screened for various thyroid diseases.

RESULTS

Mean age at exposure (± SD) was 8.2 ± 5.0 years. Mean (median) estimated 131I thyroid dose was 0.54 (0.23) Gy (range, 0.001-26.6 Gy). We found significant positive associations of 131I dose with hypothyroidism (mainly subclinical and antibody-negative) and serum TSH concentration. The excess odds ratio per 1 Gy for hypothyroidism was 0.34 (95% CI: 0.15, 0.62) and varied significantly by age at exposure and at examination, presence of goiter, and urban/rural residency. We found no evidence of positive associations with antibody-positive hypothyroidism, hyperthyroidism, AIT, or elevated ATPO.

CONCLUSIONS

The association between 131I dose and hypothyroidism in the Belarusian cohort is consistent with that previously reported for a Ukrainian cohort and strengthens evidence of the effect of environmental 131I exposure during childhood on hypothyroidism, but not other thyroid outcomes.

Overt and subclinical hypothyroidism: who to treat and how

Hypothyroidism denotes deficient production of thyroid hormone by the thyroid gland and can be primary (abnormality in thyroid gland itself) or secondary/central (as a result of hypothalamic or pituitary disease). The term 'subclinical hypothyroidism' is used to define that grade of primary hypothyroidism in which there is an elevated thyroid-stimulating hormone (TSH) concentration in the presence of normal serum free thyroxine (T4) and triiodothyronine (T3) concentrations. Subclinical hypothyroidism may progress to overt hypothyroidism in approximately 2-5% cases annually. All patients with overt hypothyroidism and subclinical hypothyroidism with TSH >10 mIU/L should be treated. There is consensus on the need to treat subclinical hypothyroidism of any magnitude in pregnant women and women who are contemplating pregnancy, to decrease the risk of pregnancy complications and impaired cognitive development of the offspring. However, controversy remains regarding treatment of non-pregnant adult patients with subclinical hypothyroidism and serum TSH values ≤10 mIU/L. In this subgroup, treatment should be considered in symptomatic patients, patients with infertility, and patients with goitre or positive anti-thyroid peroxidase (TPO) antibodies. Limited evidence suggests that treatment of subclinical hypothyroidism in patients with serum TSH of up to 10 mIU/L should probably be avoided in those aged >85 years. Other pituitary hormones should be evaluated in patients with central hypothyroidism, especially assessment of the hypothalamic-pituitary-adrenal axis, since hypocortisolism, if present, needs to be rectified prior to initiating thyroid hormone replacement. Levothyroxine (LT4) monotherapy remains the current standard for management of primary, as well as central, hypothyroidism. Treatment can be started with the full calculated dose for most young patients. However, treatment should be initiated at a low dose in elderly patients, patients with coronary artery disease and patients with long-standing severe hypothyroidism. In primary hypothyroidism, treatment is monitored with serum TSH, with a target of 0.5-2.0 mIU/L. In patients with central hypothyroidism, treatment is tailored according to free or total T4 levels, which should be maintained in the upper half of the normal range for age. In patients with persistently elevated TSH despite an apparently adequate replacement dose of LT4, poor compliance, malabsorption and the presence of drug interactions should be checked. Over-replacement is common in clinical practice and is associated with increased risk of atrial fibrillation and osteoporosis, and hence should be avoided.