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Chooprasertsuk N, Dejkhamron P, Unachak K, Wejaphikul K. Iatrogenic hyperthyroidism in primary congenital hypothyroidism: prevalence and predictive factors. J Pediatr Endocrinol Metab 2022; 35:1250-1256. [PMID: 36100363 DOI: 10.1515/jpem-2022-0152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 08/17/2022] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Primary congenital hypothyroidism (CH) is a preventable cause of mental retardation. Iatrogenic hyperthyroidism has occasionally been reported using the recommended LT4 dosage. Currently, information regarding iatrogenic hyperthyroidism and predictive factors for permanent hypothyroidism (P-CH) among Thai patients is lacking. The aim of this study is to determine the prevalence and factors for predicting iatrogenic hyperthyroidism at one month after LT4 initiation and for predicting P-CH in primary CH infants. METHODS This retrospective cohort study involved 87 infants with primary CH. Patients were classified by thyroid status at one month after LT4 initiation. At 3 years, patients were reevaluated after LT4 cessation and assigned as P-CH or transient CH (T-CH). Differences between groups were analyzed. RESULTS One month after LT4 initiation, 35.6% of patients were classified as having iatrogenic hyperthyroidism. An initial LT4 dose of 10.2 μg/kg/day (sensitivity 64.5%, specificity 71.4%) was a suitable cutoff value for predicting iatrogenic hyperthyroidism, wherein 55.6 and 21.6% of patients were treated with initial doses of ≥10.2 and <10.2 μg/kg/day, respectively (p=0.004). Initial LT4 dose was the only predictive factor for thyroid status after initial treatment. At reevaluation, 47.4% of patients were diagnosed with P-CH. LT4 dosage at 3 years of age was significantly higher in patients with P-CH (3.3 vs. 2.85 μg/kg/day, p=0.02) and the only relevant factor for predicting P-CH. CONCLUSIONS Iatrogenic hyperthyroidism is common among infants with primary CH when treated with the recommended LT4 dosage. LT4 dose was the only factor for predicting iatrogenic hyperthyroidism after LT4 initiation and the diagnosis of P-CH.
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Affiliation(s)
- Nuanpan Chooprasertsuk
- Division of Endocrinology and Metabolism, Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Prapai Dejkhamron
- Division of Endocrinology and Metabolism, Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Kevalee Unachak
- Division of Endocrinology and Metabolism, Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Karn Wejaphikul
- Division of Endocrinology and Metabolism, Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
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Lacámara N, Lecumberri B, Barquiel B, Escribano A, González-Casado I, Álvarez-Escolá C, Aleixandre-Blanquer F, Morales F, Alfayate R, Bernal-Soriano MC, Miralles R, Yildirim Simsir I, Özgen AG, Bernal J, Berbel P, Moreno JC. Identification of Resistance to Exogenous Thyroxine in Humans. Thyroid 2020; 30:1732-1744. [PMID: 32498666 DOI: 10.1089/thy.2019.0825] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Background: Thyroxine (T4) to triiodothyronine (T3) deiodination in the hypothalamus/pituitary is mediated by deiodinase type-2 (D2) activity. Dio2(-/-) mice show central resistance to exogenous T4. Patients with resistance to exogenous thyroxine (RETH) have not been described. The aim of this study was to identify hypothyroid patients with thyrotropin (TSH) unresponsiveness to levothyroxine (LT4) and to characterize the clinical, hormonal, and genetic features of human RETH. Methods: We investigated hypothyroid patients with elevated TSH under LT4 treatment at doses leading to clinical and/or biochemical hyperthyroidism. TSH and free T4 (fT4) were determined by chemiluminescence, and total T4, T3, and reverse T3 (rT3) by radioimmunoassay. TSH/fT4 ratio at inclusion and T3/T4, rT3/T4, and T3/rT3 ratios at follow-up were compared with those from patients with resistance to thyroid hormone (RTH) due to thyroid hormone receptor-β (THRB) mutations. DIO2, including the Ala92-D2 polymorphism, selenocysteine binding protein 2 (SECISBP2), and THRB were fully sequenced. Results: Eighteen hypothyroid patients (nine of each sex, 3-59 years) treated with LT4 showed elevated TSH (15.5 ± 4.7 mU/L; reference range [RR]: 0.4-4.5), fT4 (20.8 ± 2.4 pM; RR: 9-20.6), and TSH/fT4 ratio (0.74 ± 0.25; RR: 0.03-0.13). Despite increasing LT4 doses from 1.7 ± 1.0 to 2.4 ± 1.7 μg/kg/day, TSH remained elevated (6.9 ± 2.7 mU/L). Due to hyperthyroid symptoms, LT4 doses were reduced, and TSH increased again to 7.9 ± 3.2 mU/L. In the euthyroid/hyperthyrotropinemic state, T3/T4 and T3/rT3 ratios were decreased (9.2 ± 2.4, RR: 11.3-15.3 and 2.5 ± 1.4, RR: 7.5-8.5, respectively) whereas rT3/T4 was increased (0.6 ± 0.2; RR: 0.43-0.49), suggesting reduced T4 to T3 and increased T4 to rT3 conversion. These ratios were serum T4-independent and were not observed in RTH patients. Genetic testing was normal. The Ala92-D2 polymorphism was present in 7 of 18 patients, but the allele dose did not correlate with RETH. Conclusions: Human RETH is characterized by iatrogenic thyrotoxicosis and elevated TSH/fT4 ratio. In the euthyroid/hyperthyrotropinemic state, it is confirmed by decreased T3/T4 and T3/rT3 ratios, and elevated rT3/T4 ratio. This phenotype may guide clinicians to consider combined T4+T3 therapy in a targeted fashion. The absence of germline DIO2 mutations suggests that aberrant post-translational D2 modifications in pituitary/hypothalamus or defects in other genes regulating the T4 to T3 conversion pathway could be involved in RETH.
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Affiliation(s)
- Nerea Lacámara
- Thyroid Molecular Laboratory, Institute for Medical and Molecular Genetics (INGEMM), La Paz University Hospital, Autonomous University of Madrid, Madrid, Spain
- The Rare Diseases Networking Biomedical Research Centre (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | | | - Beatriz Barquiel
- Department of Endocrinology, La Paz University Hospital, Madrid, Spain
| | - Arancha Escribano
- Department of Pediatric Endocrinology, Virgen de la Arrixaca University Hospital, Murcia, Spain
| | | | | | | | - Francisco Morales
- Department of Endocrinology, Virgen Del Rocío University Hospital, Sevilla, Spain
| | - Rocío Alfayate
- Clinical Chemistry Department, Alicante University Hospital, Alicante, Spain
| | | | - Raquel Miralles
- Department of Endocrinology, Alicante University Hospital, Alicante, Spain
| | - Ilgin Yildirim Simsir
- Department of Endocrinology and Metabolism Disorders, Ege University Medical Faculty, Izmir, Turkey
| | - Ahmet Gökhan Özgen
- Department of Endocrinology and Metabolism Disorders, Ege University Medical Faculty, Izmir, Turkey
| | - Juan Bernal
- Department of Endocrine and Nervous System, Instituto de Investigaciones Biomédicas, CSIC, and CIBERER Instituto de Salud Carlos III, Madrid, Spain
| | - Pere Berbel
- Department of Histology and Anatomy, Faculty of Medicine, Universidad Miguel Hernández de Elche, Alicante, Spain
| | - Jose Carlos Moreno
- Thyroid Molecular Laboratory, Institute for Medical and Molecular Genetics (INGEMM), La Paz University Hospital, Autonomous University of Madrid, Madrid, Spain
- The Rare Diseases Networking Biomedical Research Centre (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
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Abstract
INTRODUCTION Hypothyroidism is currently a condition that can be treated, but not cured. Although levothyroxine reverses stigmata of hypothyroidism in most individuals, some patients feel dissatisfied with 'monotherapy', and this has stimulated interest in 'combination therapy' with both levothyroxine and liothyronine. AREAS COVERED A search of PubMed was conducted using terms including hypothyroidism, treatment, benefits, risks, and safety. Based on the articles identified, the body of evidence regarding the efficacy of traditional levothyroxine is reviewed. Concerns with levothyroxine therapy including impaired quality of life in treated patients, thyroxine-predominant hormone ratios, and inadvertent iatrogenic thyroid disease are discussed. The trials of combination therapy performed since 1999 were reviewed. The heterogeneity of these trials, both in terms of design and results, is discussed. The potential for new trials to determine whether combination therapy can reverse the dissatisfaction associated with monotherapy, while avoiding non-physiologic hormone ratios, inadvertent thyrotoxicosis, and unacceptable side effects is discussed. Expert commentary: Research regarding which therapy fully reverses hypothyroidism at a tissue and cellular level is ongoing. The field would be advanced by the development of an extended release preparation of liothyronine. In the future regeneration of functional thyroid follicles from stem cells may offer hope for curing hypothyroidism.
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