End‐organ Responses to Thyroxine Therapy in Subclinical Hypothyroidism

Bell, G. H.; Todd, W. T. A.; Forfar, J. C.; Martyn, Christopher; Wathen, C G; Gow, S M; Riemersma, R.A.; Toft, A. D.

doi:10.1111/j.1365-2265.1985.tb01068.x

Cited by 107 publications

(38 citation statements)

References 32 publications

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“…These results are in accordance with those of the small number of published reports about the effect of L-T4 treatment on lipoprotein and apolipoprotein fractions in patients with subclinical hypothyroidism [25,26]. But other studies have failed to demonstrate significant changes in total cholesterol following L-T4 treatment [27,28]. These conflicting results may be explained by the difference in definition of subclinical hypothyroidism and/or the characteristics (sex, age, BMI) of patients and control groups.…”

Section: Discussionsupporting

confidence: 51%

Lipoprotein(a) Concentration in Subclinical Hypothyroidism Before and After Levo-Thyroxine Therapy.

et al. 1996

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Abstract. Subclinical hypothyroidism is a frequent disorder in populations and has been shown to be a risk factor for coronary heart disease (CHD). Less is known about the contribution of lipoprotein (a) [Lp(a)] to the development of CHD in this disorder. Therefore this study was designed to evaluate Lp(a) and other lipoprotein concentrations before and after L-T4 therapy in 20 patients with subclinical hypothyroidism and 20 normal healthy subjects matched for sex, age and BMI. In the basal state of subclinical hypothyroidism, a significant increase in total cholesterol, LDL-cholesterol and apolipoprotein (apo) B concentrations was observed in patients compared with those in the control group. The mean Lp(a) concentration before treatment was 163 ± 15 mg/L. This is slightly but not significantly higher than those in the control group (131 ± 15 mg/L). Treatment of subclinical hypothyroidism with a low dose of L-T4 (25 ug daily) for 3 months after restoration of euthyroidism led to decreases in levels of Lp(a) from 163 mg/L to 126 mg/L (23% reduction, P<0.001), total cholesterol from 5.5 mmol/L to 5.1 mmol/L (7% reduction, P<0.001), LDL-cholesterol from 4.14 mmol/L to 3.63 mmol/L (12%, P<0.001), and apo B from 98 mg/dL to 86 mg/dL (12% reduction, P<0.05), but triglyceride, HDL-cholesterol and apo A-I concentrations were unchanged. These data suggest that L-T4 replacement therapy in patients with subclinical hypothyroidism has beneficial effects on the lipid profile since L-T4 replacement therapy lowered the concentrations of Lp(a) and other atherogenic lipid particles. [7,8]. The Lp(a) lipid composition is similar to that of LDL, but the protein composition is different, consisting of two major proteins, apolipoproteins (apo) B 100 and apo (a) attached to each other by a disulfide bridge [9]. Lp(a) is closely correlated with a high risk for CHD [10,11]. Metabolism of Lp(a) is largely unknown; its sites of degradation and the factors affecting its plasma levels are not fully understood. Diets and most drugs that decrease LDL cholesterol levels do not substantially alter Lp(a) levels [12] except the use of neomycin in combination with nicotinic acid [13].Recently, several reports have been published

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Section: Discussionsupporting

confidence: 51%

Lipoprotein(a) Concentration in Subclinical Hypothyroidism Before and After Levo-Thyroxine Therapy.

et al. 1996

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“…It is probably due to thyroid autoimmunity, which is known to increase with age as reported in the Wickham survey. 13 Besides, prevalence was more in females and increased with age, which is similar to that observed by Parle et al 14 Prevalence was also more in postmenopausal women. But in this study TSH level showed a gradual decrease as the age advances whereas most of the TPOAb positive people are in the age group of 26-30 years of age.…”

Section: Discussionsupporting

confidence: 78%

Study of Antithyroid Peroxidase Antibodies in People with Normal Range Thyroid Stimulating Hormone

Sam¹,

Mammen²

2017

jmscr

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“…The results include a wide range of cardiac abnormalities also by using radionuclide ventriculography. Foldes et al (36) found a lower LV ejection fraction in SH than in euthyroid controls, both at rest and during physical exercise, whereas Bell et al (37) reported an LV ejection fraction decrease only during maximal exercise. These discrepancies might be in part related to the different selection (age, sex distribution, and inclusion of patients with previous hyperthyroidism or unstable SH), to the different diagnostic criteria (too wide range of TSH levels) and to the impossibility of defining the onset and length of thyroid failure in the majority of assessed populations.…”

Section: Discussionmentioning

confidence: 99%

Left Ventricular Myocardial Impairment in Subclinical Hypothyroidism Assessed by a New Ultrasound Tool: Pulsed Tissue Doppler

Vitale¹,

Galderisi

Lupoli³

et al. 2002

The Journal of Clinical Endocrinology &Amp; Metabolism

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S UBCLINICAL HYPOTHYROIDISM (SH) is a commondisorder characterized by increased serum TSH and its response to TRH, whereas serum free T 4 (FT 4 ) and free T 3 (FT 3 ) concentrations are within the normal range for the general population (1, 2). In view of the minor thyroid hormone secretion impairment, it is predictable that metabolic and organ function indexes of SH will show only marginal alterations. Nevertheless, such changes may be clinically relevant when they affect target organs over a period of several years (3). In particular, heart and vessels are very sensitive to thyroid hormones, as cardiovascular disorders are often associated with both overt hypothyroidism and hyperthyroidism (4 -8). Several noninvasive techniques (9 -16) have been used to assess cardiac involvement in SH, but all of them provide information about left ventricular (LV) global chamber function without exploring changes occurring at the level of the regional myocardial walls.Pulsed tissue Doppler (TD) is a new noninvasive ultrasound tool that allows measurement of myocardial regional wall motion. Although standard echocardiography collects data about cardiac function either from parameters measured from the blood-myocardial boundaries or from Doppler flow, TD has the peculiarity of directly measuring velocities and time intervals of myocardium by placing a sample volume within the chosen myocardial walls. It is noteworthy that TD evaluation is performed on line during a simple echocardiographic examination by modifying filter settings and reducing velocity ranges of the standard Doppler signal (17)(18)(19).On these grounds the present study was designed to investigate myocardial regional function in SH by using pulsed TD to identify possible LV myocardial systolic and diastolic involvement in relation to a reference population of euthyroid healthy subjects. Subjects and Methods Study protocolTwenty female patients (mean age Ϯ sd, 38.5 Ϯ 12.4 yr) with newly diagnosed, untreated, autoimmune primary SH and no previous history of thyrotoxicosis were included in the study. SH was diagnosed in those cases where TSH values were above normal and associated with a supranormal response to TRH (change in TSH, Ͼ30 mU/liter) and FT 3 and FT 4 levels in the lower limit of the normal range. Only patients with TSH and thyroid hormone levels stable for at least 6 months before enrolment were included. TSH and thyroid hormones were considered stable if their variations were lower than 20% in 3 consecutive evaluations performed in the 6 months preceding the current study. Twenty female healthy subjects, recruited among the staff and relatives of medical doctors attending the present study, were included in the control group. All subjects gave informed consent, and the study was approved by the institutional ethical committee. Exclusion criteria were history of any acquired and/or congenital cardiac disease; arterial systemic hypertension; diabetes mellitus; respiratory, hematological, liver, and/or kidney diseases; pregnancy; administration of cardia...

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End‐organ Responses to Thyroxine Therapy in Subclinical Hypothyroidism

Cited by 107 publications

References 32 publications

Lipoprotein(a) Concentration in Subclinical Hypothyroidism Before and After Levo-Thyroxine Therapy.

Lipoprotein(a) Concentration in Subclinical Hypothyroidism Before and After Levo-Thyroxine Therapy.

Study of Antithyroid Peroxidase Antibodies in People with Normal Range Thyroid Stimulating Hormone

Left Ventricular Myocardial Impairment in Subclinical Hypothyroidism Assessed by a New Ultrasound Tool: Pulsed Tissue Doppler

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