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Yu Y, Hou Y, Dang Y, Zhu X, Li Z, Chen H, Xiang M, Li Z, Hu G. Exposure of adult zebrafish (Danio rerio) to Tetrabromobisphenol A causes neurotoxicity in larval offspring, an adverse transgenerational effect. JOURNAL OF HAZARDOUS MATERIALS 2021; 414:125408. [PMID: 33647619 DOI: 10.1016/j.jhazmat.2021.125408] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 02/08/2021] [Accepted: 02/09/2021] [Indexed: 06/12/2023]
Abstract
Tetrabromobisphenol A (TBBPA) is one of the most extensively used brominated flame retardants and is universally detected in the environment. However, information related to its transgenerational toxicity is sparse. Using zebrafish as a study model, adult fish were exposed to TBBPA at different concentrations (0, 3, 30, or 300 μg/L) for 42 d and then, the exposed adults were spawned in TBBPA-free water. The neurobehavior of adults and larval offspring was evaluated, and the levels of thyroxine (T4), triiodothyronine (T3) and neurotransmitters (acetylcholine, dopamine and gamma-aminobutyric acid) were quantified in larvae and embryos. Our results showed that TBBPA was detected in embryo and the locomotor activity of larval offspring was significantly reduced, suggesting that TBBPA can transfer to offspring and result in neurotoxicity in larval offspring. Furthermore, a reduction in T3 levels was observed in both the larvae and embryos. We also found a significantly decreased content of dopamine in larval offspring, accompanied by downregulated mRNA expression of rdr2b and drd3. Our results demonstrated that TBBPA can be transferred to offspring embryos, and subsequently induce neurotoxicity in larval offspring by affecting the amount of T3 transferred from the parents to embryos and the production of dopamine in larvae.
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Affiliation(s)
- Yunjiang Yu
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China.
| | - Yunbo Hou
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China; College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang 443002, China
| | - Yao Dang
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China.
| | - Xiaohui Zhu
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China
| | - Zhenchi Li
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China
| | - Haibo Chen
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China; Institute for Environmental Pollution and Health, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China
| | - Mingdeng Xiang
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China
| | - Zongrui Li
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China
| | - Guocheng Hu
- State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou 510655, China
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Abstract
Background: The basis for the treatment of hypothyroidism with levothyroxine (LT4) is that humans activate T4 to triiodothyronine (T3). Thus, while normalizing serum thyrotropin (TSH), LT4 doses should also restore the body's reservoir of T3. However, there is evidence that T3 is not fully restored in LT4-treated patients. Summary: For patients who remain symptomatic on LT4 therapy, clinical guidelines recommend, on a trial basis, therapy with LT4+LT3. Reducing the LT4 dose by 25 mcg/day and adding 2.5-7.5 mcg liothyronine (LT3) once or twice a day is an appropriate starting point. Transient episodes of hypertriiodothyroninemia with these doses of LT4 and LT3 are unlikely to go above the reference range and have not been associated with adverse drug reactions. Trials following almost a 1000 patients for almost 1 year indicate that similar to LT4, therapy with LT4+LT3 can restore euthyroidism while maintaining a normal serum TSH. An observational study of 400 patients with a mean follow-up of ∼9 years did not indicate increased mortality or morbidity risk due to cardiovascular disease, atrial fibrillation, or fractures after adjusting for age when compared with patients taking only LT4. Desiccated thyroid extract (DTE) is a form of combination therapy in which the LT4/LT3 ratio is ∼4:1; the mean daily dose of DTE needed to normalize serum TSH contains ∼11 mcg T3, but some patients may require higher doses. The DTE remains outside formal FDA oversight, and consistency of T4 and T3 contents is monitored by the manufacturers only. Conclusions: Newly diagnosed hypothyroid patients should be treated with LT4. A trial of combination therapy with LT4+LT3 can be considered for those patients who have unambiguously not benefited from LT4.
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Affiliation(s)
- Thaer Idrees
- Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, University of Chicago, Chicago, Illinois, USA
| | - Scott Palmer
- Department of Medicine, Rush University Medical Center, Chicago, Illinois, USA
| | - Rui M.B. Maciel
- Division of Endocrinology, Universidade Federal de Sao Paulo, Sao Paulo, Brazil
| | - Antonio C. Bianco
- Section of Adult and Pediatric Endocrinology, Diabetes and Metabolism, University of Chicago, Chicago, Illinois, USA
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Routine free thyroxine reference intervals are suboptimal for monitoring children on thyroxine replacement therapy and target intervals need to be assay-specific. Sci Rep 2019; 9:19080. [PMID: 31836869 PMCID: PMC6910984 DOI: 10.1038/s41598-019-55690-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 12/02/2019] [Indexed: 02/02/2023] Open
Abstract
Central hypothyroidism is a condition where there is (qualitatively or quantitatively) TSH deficiency, leading to reduced thyroid hormone production. In such patients, serum TSH does not accurately reflect the adequacy of thyroxine replacement, as the log-linear relationship between thyrotropin (TSH) and free thyroxine (FT4) is lost. We aimed to prospectively determine the optimal physiological FT4 treatment range for children treated for primary hypothyroidism, based on their serum TSH concentrations. This information could be used to guide optimal therapy for all children on thyroxine replacement, including those with central hypothyroidism. In total, sixty children (median age: 11 years, range: 11 months to 18 years) were recruited over 21 months. They were prescribed a stable dose of thyroxine for at least 6-8 weeks prior to a thyroid function test that consisted of serum TSH, FT4 and free triiodothyronine (FT3) measurements. The serum sample for the thyroid function tests was collected before ingestion of the daily dose, i.e. the trough concentration, and measured using Beckman Coulter UniCel DxI 800 instrument, Siemens Advia Centaur, Roche Cobas, Abbott Architect, Ortho Clinical Diagnostics Vitros 5600 (Ortho-Clinical Diagnostics, Raritan, NJ) platforms. The FT4 and FT3 reference intervals showed significant inter-method difference. The lower limit of the FT4 reference intervals were generally shifted mildly higher when the TSH concentration of the children were restricted from 0.5-5.0 mIU/L to 0.5-2.5 mIU/L. By contrast, the upper limit of the FT3 and FT4 reference intervals were relatively stable for the different TSH concentrations. Assay-specific target ranges for optimal thyroxine therapy are required until FT4 assay standardisation is realised.
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Zhu B, Zhao G, Yang L, Zhou B. Tetrabromobisphenol A caused neurodevelopmental toxicity via disrupting thyroid hormones in zebrafish larvae. CHEMOSPHERE 2018; 197:353-361. [PMID: 29407805 DOI: 10.1016/j.chemosphere.2018.01.080] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/14/2018] [Accepted: 01/16/2018] [Indexed: 05/27/2023]
Abstract
Tetrabromobisphenol A (TBBPA), one of the most widely used brominated flame retardants (BFRs), has resulted in worldwide environmental contamination. TBBPA has been reported as a thyroid endocrine disruptor and a potential neurotoxicant. However, the underlying mechanism is still not clear. In this study, zebrafish (Danio rerio) embryos (2 h post-fertilization, hpf) were exposed to different concentrations of TBBPA (50, 100, 200 and 400 μg/L) alone or in combination with 3,3',5-triiodo-l-thyronine (T3, 20 μg/L + TBBPA, 200 μg/L). The results confirmed that TBBPA could evoke thyroid disruption by observations of increased T4 contents and decreased T3 contents, accompanied by up-regulated tshβ, tg mRNA and down-regulated ttr and trβ mRNA levels in zebafish larvae. TBBPA-induced neurodevelopmental toxicity was also indicated by down-regulated transcription of genes related to central nervous system (CNS) development (e.g., α1-tubulin, mbp and shha), and decreased locomotor activity and average swimming speed. Our results further demonstrated that treatment with T3 could reverse or eliminate TBBPA-induced effects on thyroidal and neurodevelopmental parameters. Given the above, we hypothesize that the observed neurodevelopmental toxicity in the present study could be attributed to the thyroid hormone disruptions by TBBPA.
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Affiliation(s)
- Biran Zhu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; Department of Basic Medicine, Hubei University of Chinese Medicine, Wuhan, 430065, China
| | - Gang Zhao
- Department of Basic Medicine, Hubei University of Chinese Medicine, Wuhan, 430065, China
| | - Lihua Yang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
| | - Bingsheng Zhou
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
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5
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Bahroo SL. The Never Ending Debate. PHYSICIAN ASSISTANT CLINICS 2017. [DOI: 10.1016/j.cpha.2016.08.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
Thyroid hormone deficiency can have important repercussions. Treatment with thyroid hormone in replacement doses is essential in patients with hypothyroidism. In this review, we critically discuss the thyroid hormone formulations that are available and approaches to correct replacement therapy with thyroid hormone in primary and central hypothyroidism in different periods of life such as pregnancy, birth, infancy, childhood, and adolescence as well as in adult patients, the elderly, and in patients with comorbidities. Despite the frequent and long term use of l-T4, several studies have documented frequent under- and overtreatment during replacement therapy in hypothyroid patients. We assess the factors determining l-T4 requirements (sex, age, gender, menstrual status, body weight, and lean body mass), the major causes of failure to achieve optimal serum TSH levels in undertreated patients (poor patient compliance, timing of l-T4 administration, interferences with absorption, gastrointestinal diseases, and drugs), and the adverse consequences of unintentional TSH suppression in overtreated patients. Opinions differ regarding the treatment of mild thyroid hormone deficiency, and we examine the recent evidence favoring treatment of this condition. New data suggesting that combined therapy with T3 and T4 could be indicated in some patients with hypothyroidism are assessed, and the indications for TSH suppression with l-T4 in patients with euthyroid multinodular goiter and in those with differentiated thyroid cancer are reviewed. Lastly, we address the potential use of thyroid hormones or their analogs in obese patients and in severe cardiac diseases, dyslipidemia, and nonthyroidal illnesses.
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Affiliation(s)
- Bernadette Biondi
- Department of Clinical Medicine and Surgery (B.B.), University of Naples Federico II, 80131 Naples, Italy; and Washington Hospital Center (L.W.), Washington, D.C. 20010
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7
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Persani L, Bonomi M. Uncertainties in endocrine substitution therapy for central endocrine insufficiencies: hypothyroidism. HANDBOOK OF CLINICAL NEUROLOGY 2014; 124:397-405. [PMID: 25248602 DOI: 10.1016/b978-0-444-59602-4.00027-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
In patients with primary hypothyroidism (PH), L-T4 replacement therapy can safely be adjusted to the individual needs by testing serum thyrotropin (TSH) concentration exclusively. Central hypothyrodism (CeH) is a particular hypothyroid condition due to an insufficient stimulation by TSH of an otherwise normal thyroid gland. CeH is about 1000-fold rarer than PH and raises several challenges for clinicians, mainly because they cannot rely on the systematic use of the reflex TSH strategy for diagnosis or therapy monitoring. Therefore, L-T4 replacement in CeH should rely on the combined evaluation of several biochemical and clinical parameters in order to overcome the lack of accuracy of the single index. The management of CeH replacement is further complicated by the frequent combination with other pituitary deficiencies and their treatment.
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Affiliation(s)
- Luca Persani
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy; Division of Endocrine and Metabolic Diseases, San Luca Hospital, Istituto Auxologico Italiano, Milan, Italy.
| | - Marco Bonomi
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy; Division of Endocrine and Metabolic Diseases, San Luca Hospital, Istituto Auxologico Italiano, Milan, Italy
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8
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Carswell JM, Gordon JH, Popovsky E, Hale A, Brown RS. Generic and brand-name L-thyroxine are not bioequivalent for children with severe congenital hypothyroidism. J Clin Endocrinol Metab 2013; 98:610-7. [PMID: 23264396 PMCID: PMC3565118 DOI: 10.1210/jc.2012-3125] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT In the United States, generic substitution of levothyroxine (L-T(4)) by pharmacists is permitted if the formulations are deemed to be bioequivalent by the Federal Drug Administration, but there is widespread concern that the pharmacokinetic standard used is too insensitive. OBJECTIVE We aimed to evaluate the bioequivalence of a brand-name L-T(4) (Synthroid) and an AB-rated generic formulation (Sandoz, Princeton, NJ) in children with severe hypothyroidism. DESIGN This was a prospective randomized crossover study in which patients received 8 weeks of one L-T(4) formulation followed by 8 weeks of the other. SETTING The setting was an academic medical center. PATIENTS Of 31 children with an initial serum TSH concentration >100 mU/L, 20 had congenital hypothyroidism (CH), and 11 had autoimmune thyroiditis. MAIN OUTCOME MEASURES The primary endpoint was the serum TSH concentration. Secondary endpoints were the free T(4) and total T(3) concentrations. RESULTS The serum TSH concentration was significantly lower after 8 weeks of Synthroid than after generic drug (P = .002), but thyroid hormone levels did not differ significantly. Subgroup analysis revealed that the difference in TSH was restricted to patients with CH (P = .0005). Patients with CH required a higher L-T(4) dose (P < .0004) and were younger (P = .003) but were not resistant to thyroid hormone; 15 of 16 CH patients had severe thyroid dysgenesis or agenesis on imaging. The response to generic vs brand-name preparation remained significant when adjusted for age. CONCLUSIONS Synthroid and an AB-rated generic L-T(4) are not bioequivalent for patients with severe hypothyroidism due to CH, probably because of diminished thyroid reserve. It would therefore seem prudent not to substitute L-T(4) formulations in patients with severe CH, particularly in those <3 yr of age. Our results may have important implications for other severely hypothyroid patients in whom precise titration of L-T(4) is necessary.
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Affiliation(s)
- Jeremi M Carswell
- Division of Endocrinology, Boston Children's Hospital, 300 Longwood Avenue, Boston, Massachusetts 02115, USA
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9
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Persani L. Clinical review: Central hypothyroidism: pathogenic, diagnostic, and therapeutic challenges. J Clin Endocrinol Metab 2012; 97:3068-78. [PMID: 22851492 DOI: 10.1210/jc.2012-1616] [Citation(s) in RCA: 178] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
CONTEXT Central hypothyroidism (CH) is a particular hypothyroid condition due to an insufficient stimulation by TSH of an otherwise normal thyroid gland. This condition raises several challenges for clinicians; therefore, a review of the most relevant findings on CH epidemiology, pathogenesis, and clinical management has been performed. METHODOLOGY The relevant papers were selected by a PubMed search using appropriate key words. MAIN FINDINGS CH can be the consequence of various disorders affecting either the pituitary gland or the hypothalamus, but most frequently affecting both of them. CH is about 1000-fold rarer than primary hypothyroidism. Except for the neonatal CH due to biallelic TSHβ mutations, the thyroid hormone defect is rarely as profound as can be observed in some primary forms. In contrast with primary hypothyroidism, CH is most frequently characterized by low/normal TSH levels, and adequate thyroid hormone replacement is associated with the suppression of residual TSH secretion. Thus, CH often represents a clinical challenge because physicians cannot rely on the systematic use of the "reflex TSH strategy." The clinical management of CH is further complicated by the frequent combination with other pituitary deficiencies and their substitution.
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Affiliation(s)
- Luca Persani
- Department of Clinical Sciences and Community Health, University of Milan, 20122 Milan, Italy.
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10
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Space-time clustering of elevated thyroid stimulating hormone levels. Eur J Epidemiol 2011; 26:405-11. [PMID: 21476081 DOI: 10.1007/s10654-011-9571-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Accepted: 03/23/2011] [Indexed: 10/18/2022]
Abstract
Previous studies of congenital hypothyroidism (CHT) have reported an increasing incidence which may suggest that environmental factors play an aetiological role. If so, then cases may exhibit space-time clustering, where cases occur at similar times and close proximities to other cases. In this study we investigated whether space-time clustering of elevated thyroid stimulating hormone (TSH) in newborns exists. All infants born in the Northern Region of England are screened by measuring levels of circulating TSH using a blood spot assay. Data on 207 cases of elevated TSH values, as a proxy for CHT, in newborns born from 1994 to 2006 inclusive were available and analysed using rigorous space-time clustering statistical methods. Analysis showed statistically significant evidence of space-time clustering. The strength of clustering was most marked for cases born within 0.1-0.7 year (1-8 months) of one another. This is the first study to find significant space-time clustering of cases of elevated TSH levels in newborns, a surrogate for space-time clustering of CHT. Whilst the reasons for the clustering are unclear, it would appear from this analysis that transient environmental exposures are likely to be involved, although environmental determinants of genetic mutations and epigenetic factors cannot be ruled out. Further research is required to a) validate these results in other populations and b) to assess in more detail the potential environmental determinants of increased CHT risk.
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Pearce MS, Korada M, Day J, Turner S, Allison D, Kibirige M, Cheetham TD. Increasing Incidence, but Lack of Seasonality, of Elevated TSH Levels, on Newborn Screening, in the North of England. J Thyroid Res 2010; 2010:101948. [PMID: 21048833 PMCID: PMC2956968 DOI: 10.4061/2010/101948] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Accepted: 12/15/2009] [Indexed: 12/31/2022] Open
Abstract
Previous studies of congenital hypothyroidism have suggested an increasing incidence and seasonal variation in incidence, which may suggest nongenetic factors involved in aetiology. This study describes the incidence of elevated thyroid stimulating hormone (TSH) values in newborns, a surrogate for congenital hypothyroidism, measured as part of the screening programme for congenital hypothyroidism, over an eleven-year period (1994-2005), and assesses whether seasonal variation exists. All infants born in the Northern Region of England are screened by measuring levels of circulating TSH using a blood spot assay. Data on all 213 cases born from 1994 to 2005 inclusive were available. Annual incidence increased significantly from 37 per 100,000 in 1994 to a peak of 92.8 per 100,000 in 2003. There was no evidence of seasonal variation in incidence. The reasons for the increasing incidence are unclear, but do not appear to involve increasing exposure to seasonally varying factors or changes in measurements methods.
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Affiliation(s)
- Mark S Pearce
- Institute of Health and Society, Newcastle University, Newcastle upon Tyne NE1 4LP, UK
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12
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Abstract
Central hypothyroidism (CH) is a rare cause of hypothyroidism due to an insufficient stimulation of an otherwise normal thyroid gland and it is caused by either pituitary (secondary hypothyroidism) or hypothalamic (tertiary hypothyroidism) defects. The diagnosis of CH is usually suggested by the finding of lowered thyroid hormone concentrations, associated with inappropriately low/ normal TSH levels. Restoration and maintenance of euthyroidism represent the therapeutic goals in all forms of CH. On these basis, the vast majority of patients with CH is treated with standard levo-thyroxine (L-T4) therapy which is tailored according to FT4 circulating levels that should be maintained in the normal range.
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Affiliation(s)
- Andrea Lania
- Department of Medical Sciences, Fondazione Ospedale Maggiore Policlinico IRCCS, University of Milan, Milan, Italy
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13
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Abstract
The term 'subclinical hypothyroidism' applies to patients who have mildly increased levels of serum thyrotropin hormone (TSH) and normal levels of thyroxine and liothyronine (triiodiothyronine). This very common condition, also called 'mild thyroid failure', accounts for 75% of patients who have increased serum TSH. For patients with sustained increases above 10 mIU/L, there is uniform agreement that thyroxine therapy is indicated. Therapy for milder forms of hypothyroidism is controversial. Some randomized clinical trials favor therapy for mild thyroid failure, but they are inconclusive because they lack stratification for the subgroup of patients with TSH levels below 10 mIU/L. For this subgroup, we recommend individualized management. The presence of goiter, positive thyroperoxidase (TPO) antibodies, manic-depressive disorder, fertility problems, or pregnancy or the anticipation of pregnancy favors the initiation of therapy. Positive TPO antibodies are a strong indication for therapy because of the high likelihood in these patients of progression to overt hypothyroidism; patients who are already receiving thyroxine should have adjustments of their dosage. Children and adolescents with mild thyroid failure should also be treated because of possible adverse effects on growth and development. It has been suggested that subclinical hypothyroidism is a cardiovascular risk factor, however further investigation is needed. The controversy surrounding therapy will not be resolved until more randomized studies are available for the subgroup of patients with TSH <10 mIU/L, and until the question of cardiovascular risk factors is further clarified.
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Affiliation(s)
- Vahab Fatourechi
- Division of Endocrinology, Metabolism, Diabetes, Nutrition, and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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14
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Green WL. New questions regarding bioequivalence of levothyroxine preparations: a clinician's response. AAPS JOURNAL 2005; 7:E54-8. [PMID: 16146330 PMCID: PMC2751497 DOI: 10.1208/aapsj070107] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A recent decision by the Food and Drug Administration (FDA) to declare various brands of levothyroxine bioequivalent has provoked objections from several physicians' organizations. These organizations assert that the method of testing bioequivalence is flawed, and that indiscriminate switching among preparations could lead to serious instances of undertreatment and overtreatment of hypothyroid patients. In this review we first list common indications for thyroid hormone administration, distinguishing its use as replacement therapy in hypothyroidism from its use to suppress thyrotropin (TSH) secretion in cases of thyroid cancer, nodules, and goiter. The dangers associated with changing to a preparation with different bioavailability are summarized, noting the particular danger of giving a more active preparation to a patient receiving TSH-suppressive doses of levothyroxine. However, these dangers are part of a larger problem: there are data showing that large numbers of patients are already receiving an improper dosage of levothyroxine, as judged from measurements of serum TSH. The recent history of FDA actions concerning levothyroxine bioequivalence and the arguments of those in disagreement are summarized. The immediate response to these problems should be better education of both patients and physicians. It is also recommended that there be further discussion of the problems in determining bioequivalence, and that consideration be given to more accurate and clinically relevant methods. Such methods should include assessment of the changes in TSH induced by each preparation in athyrotic patients.
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Affiliation(s)
- William L Green
- Division of Endocrinology, Metabolism, and Nutrition, VA Puget Sound Health Care System, Seattle, WA 98108, USA.
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15
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Fardella C, Gloger S, Figueroa R, Santis R, Gajardo C, Salgado C, Barroilhet S, Foradori A. High prevalence of thyroid abnormalities in a Chilean psychiatric outpatient population. J Endocrinol Invest 2000; 23:102-6. [PMID: 10800763 DOI: 10.1007/bf03343687] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The aim of the present study was to establish the prevalence of thyroid disturbances in patients consulting for panic and mood disorders. These data may be relevant because thyroid functional alterations affect the success of treatment in these pathologies. We studied prospectively 268 psychiatric outpatients (204 females and 64 males) diagnosed by DSM-IV criteria. We excluded patients with addictive disorders and major medical disease. We measured TSH, Free T4 (FT4) and antimicrosomal antibodies (AMA). We diagnosed classical hypothyroidism when the TSH value was >10 microUI/ml (NV=0.25-4.3) and subclinical hypothyroidism when the TSH value was between 5-10 microUI/ml. Hyperthyroidism was diagnosed when FT4 >1.4 (NV=0.8-1.4), the TSH suppressed and the radioiodine uptake >20% (NV=5-15). Positive antimicrosomal antibodies (AMA) titres were >1:100 dilution. Hypothyroidism was diagnosed in 26/268 patients (9.7%); 10 cases corresponded to the classical form (38.5%) and 16 cases to the subclinical form (61.5%). Hyperthyroidism was found in 6/268 patients (2.2%). Normal thyroid function with positive AMA was found in 28/268 patients (10.4%). Hypothyroidism was more common in patients with mood disorders, and hyperthyroidism in patients with panic disorders. Patients with panic disorder had significant higher levels of FT4. The prevalence of positive AMA, hypothyroidism and hyperthyroidism was higher in women than men. We found a high frequency of thyroid abnormalities in a psychiatric outpatient population. These data suggests that routine evaluation of thyroid function should be considered in patients consulting for mood and panic disorders.
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Affiliation(s)
- C Fardella
- Department of Endocrinology, Faculty of Medicine, Catholic University of Chile, Santiago
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Abstract
The term "autoimmune thyroid disease" encompasses all of the autoimmune thyroid conditions, including Hashimoto's thyroiditis, Graves' disease, most cases of silent thyroiditis, and postpartum thyroiditis. Extrathyroidal manifestations (e.g., ophthalmopathy, dermopathy) can occur in Graves' disease and, less commonly, Hashimoto's thyroiditis. Spontaneous hypothyroidism is common in patients with Hashimoto's thyroiditis, and when it develops, life-long therapy with levothyroxine is needed. In the United States, most adult patients with Graves' disease are initially or eventually treated with radioiodine thyroid ablation. For transient thyroiditis involving hypothyroidism or hyperthyroidism, short-term or symptomatic therapy is adequate.
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Ferretti E, Persani L, Jaffrain-Rea ML, Giambona S, Tamburrano G, Beck-Peccoz P. Evaluation of the adequacy of levothyroxine replacement therapy in patients with central hypothyroidism. J Clin Endocrinol Metab 1999; 84:924-9. [PMID: 10084572 DOI: 10.1210/jcem.84.3.5553] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
As there are few data on the evaluation of the adequacy of levothyroxine (L-T4) therapy in patients with central hypothyroidism (CH), a prospective study was performed to assess the accuracy of various parameters in the follow-up of 37 CH patients. Total and free thyroid hormones, TSH, and a series of clinical and biochemical indexes of peripheral thyroid hormone action have been evaluated off and on L-T4 therapy. Samples were taken before the daily administration of L-T4. In all patients off therapy, clinical hypothyroidism and low levels of free T4 (FT4) were observed, whereas values of FT3, total T4, and total T3 were below the normal range in 73%, 57%, and 19% of cases, respectively. Most of the indexes of thyroid hormone action were significantly modified after L-T4 withdrawal and exhibited significant correlation with free thyroid hormone levels. During L-T4 replacement therapy, 32 patients had circulating levels of FT4 and FT3 and indexes within the normal range with a mean L-T4 daily dose of 1.5 +/- 0.3 microg/kg BW. Despite normal serum FT4, 3 patients had borderline high values of FT3 and a clear elevation of serum-soluble interleukin-2 receptor concentrations, suggesting overtreatment. Low or borderline low FT4/FT3 levels indicated undertreatment in 2 patients. The clinical parameters lack the required specificity for the diagnosis or follow-up of CH patients. The L-T4 daily dose should be established, taking into account the weight, the age, and the presence of other hormone deficiencies or pharmacological treatment of CH patients. In conclusion, our results indicate that the diagnosis of CH is reached at best by measuring TSH and FT4 concentrations. In the evaluation of the adequacy of L-T4 replacement therapy, both FT4 and FT3 serum levels together with some biochemical indexes of thyroid hormone action are all necessary to a more accurate disclosure of over- or undertreated patients.
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Affiliation(s)
- E Ferretti
- Department of Endocrinology, University La Sapienza, Rome, Italy
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Peran S, Garriga MJ, Morreale de Escobar G, Asunción M, Peran M. Increase in plasma thyrotropin levels in hypothyroid patients during treatment due to a defect in the commercial preparation. J Clin Endocrinol Metab 1997; 82:3192-5. [PMID: 9329337 DOI: 10.1210/jcem.82.10.4287] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Around mid-1995, the Molecular Endocrinology Laboratory of the Regional Hospital (Malaga, Spain) began detecting an increase in TSH levels in the serum of patients under study to control the treatment of hypothyroidism with levothyroxine. Over a period of 5 months, of a total of 467 hypothyroid patients treated with Levothyroid, 53% had TSH levels higher than 6 microU/mL. The reliability of the biochemical results was verified by duplicating 56 randomly chosen samples from all those with high TSH levels and by an external control performed in four different laboratories. The amount of levothyroxine in the tablets was analyzed by RIA, high performance liquid chromatography, and their iodine contents. The lowest levels of levothyroxine found in the 50 micrograms Levothyroid tablets were those determined by RIA, with a mean value of 32.3 micrograms, resulting in a 35.3% loss of activity. The mean value of levothyroxine found in these same tablets by high performance liquid chromatography was 39.3 micrograms, amounting to a 21.3% loss in activity. The iodine showed no significant loss in these tablets, with a mean experimental value of 48 micrograms. The commercial laboratory withdrew lot J from the market, the one in which these deficiencies were found.
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Affiliation(s)
- S Peran
- Hospital Regional de Málaga, Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Málaga, Spain.
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Marcocci C, Golia F, Vignali E, Pinchera A. Skeletal integrity in men chronically treated with suppressive doses of L-thyroxine. J Bone Miner Res 1997; 12:72-7. [PMID: 9240728 DOI: 10.1359/jbmr.1997.12.1.72] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We measured bone mineral density (BMD) (lumbar spine, femoral neck, Ward's triangle, and trochanter) in 34 men given suppressive doses of levothyroxine (L-T4) for a mean of 10.2 years. Indications for treatment were nontoxic goiter (n = 5) or thyroidectomy for differentiated thyroid cancer (n = 6) or nontoxic goiter (n = 3). Patients were followed at our institution and treated with the minimal amount of L-T4 able to suppress thyroid-stimulating hormone (TSH). At the time of evaluation, free T3 was normal in all cases, whereas free T4 was increased in 14 men (41.2%). The mean daily dose of L-T4 was 172 +/- 6 microg, and the cumulative dose of L-T4 was 673 +/- 71 mg. We found no significant difference between patients and age- and weight-matched controls in BMD (g/cm2) at any site of measurement (lumbar spine 1.144 +/- 0.12 vs. 1.168 +/- 0.15; femoral neck 0.979 +/- 0.13 vs. 1.001 +/- 0.13; Ward's triangle 0.854 +/- 0.17 vs. 0.887 +/- 0.15; and trocanther 0.852 +/- 0.13 vs. 0.861 +/- 0.13). BMD was not correlated with the duration of therapy, cumulative or mean daily dose of L-T4, serum levels of free T4, free T3, osteocalcin, and bone alkaline phosphatase. Serum calcium and osteocalcin were slightly but significantly elevated in patients compared with controls, whereas there was no difference in intact parathyroid hormone, bone alkaline phosphatase, and sex hormone-binding globulin (marker of thyroid hormone action). Our data suggest that L-T4 suppressive therapy, if carefully carried out and monitored, using the smallest dose necessary to suppress TSH secretion, has no significant effects on bone metabolism and bone mass in men.
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Affiliation(s)
- C Marcocci
- Isitituto di Endocrinologia, Università di Pisa, Tirrenia-Pisa, Italy
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Abstract
OBJECTIVE To review the management of thyroxine (T4) therapy in pregnant patients with hypothyroidism. METHODS The results of pertinent published studies are summarized, and practical recommendations are presented. RESULTS The conditions for which T4 therapy is administered during pregnancy are the same as those in nonpregnant patients: hypothyroidism, thyrotropin or thyroid-stimulating hormone (TSH) control after surgical treatment of thyroid cancer, and, in selected patients, suppression treatment for postsurgical thyroid remnants, thyroid nodules, or goiter. Untreated hypothyroidism during pregnancy can potentially cause adverse effects in both mother and fetus. Up to 75% of T4-treated women with hypothyroidism require higher doses of T4 during pregnancy than before or after conception, to maintain serum TSH levels in the normal range. Otherwise, in a substantial percentage of these women, subnormal serum free T4 levels, TSH elevations >20 microIU/L, or both will develop. The mean T4 dose needed to correct hypothyroidism during pregnancy is about 150 microg/day, but individual dose requirements vary widely. CONCLUSION The increment in T4 dose needed to normalize an increased TSH level in women taking T4 can be estimated from the serum TSH concentration during pregnancy. Increased TSH levels can appear as early as 4 to 8 weeks of gestation or as late as the third trimester. Although the optimal schedule is uncertain, assessing the TSH once each trimester seems reasonable. After pregnancy, the T4 dose should be reduced to the preconception level, and postpartum reassessment should be done at 6 to 12 weeks.
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Affiliation(s)
- M M Kaplan
- Division of Endocrinology, Department of Medicine, William, Beaumont Hospital, Royal Oak, Michigan, USA
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