Muscle strength in hyperthyroid patients before and after medical treatment

Levothyroxine Therapy in Elderly Patients With Hypothyroidism

Levothyroxine (L-T4) treatment of overt hypothyroidism can be more challenging in elderly compared to young patients. The elderly population is growing, and increasing incidence and prevalence of hypothyroidism with age are observed globally. Elderly people have more comorbidities compared to young patients, complicating correct diagnosis and management of hypothyroidism. Most importantly, cardiovascular complications compromise the usual start dosage and upward titration of L-T4 due to higher risk of decompensating cardiac ischemia and -function. It therefore takes more effort and care from the clinician, and the maintenance dose may have to be lower in order to avoid a cardiac incidence. On the other hand, L-T4 has a beneficial effect on cardiac function by increasing performance. The clinical challenge should not prevent treating with L-T4 should the patient develop e.g., cardiac ischemia. The endocrinologist is obliged to collaborate with the cardiologist on prophylactic cardiac measures by invasive cardiac surgery or medical therapy against cardiac ischemic angina. This usually allows subsequent successful treatment. Management of mild (subclinical) hypothyroidism is even more complex. Prevalent comorbidities in the elderly complicate correct diagnosis, since many concomitant morbidities can result in non-thyroidal illness, resembling mild hypothyroidism both clinically and biochemically. The diagnosis is further complicated as methods for measuring thyroid function (thyrotropin and thyroxine) vary immensely according to methodology and background population. It is thus imperative to ensure a correct diagnosis by etiology (e.g., autoimmunity) before deciding to treat. Even then, there is controversy regarding whether or not treatment of such mild forms of hypothyroidism in elderly will improve mortality, morbidity, and quality of life. This should be studied in large cohorts of patients in long-term placebo-controlled trials with clinically relevant outcomes. Other cases of hypothyroidism, e.g., medications, iodine overload or hypothalamus-pituitary-hypothyroidism, each pose specific challenges to management of hypothyroidism; these cases are also more frequent in the elderly. Finally, adherence to treatment is generally challenging. This is also the case in elderly patients, which may necessitate measuring thyroid hormones at individually tailored intervals, which is important to avoid over-treatment with increased risk of cardiac morbidity and mortality, osteoporosis, cognitive dysfunction, and muscle deficiency.

Thyroid Function and Sarcopenia: Results from the ELSA-Brasil Study

OBJECTIVES

We aimed to investigate the association of subclinical thyroid disease and thyroid hormone levels with sarcopenia and its defining components in community-dwelling middle-aged and older adults without overt thyroid dysfunction.

DESIGN

Cross-sectional study.

SETTING

Active and retired employees from public institutions located in six Brazilian cities.

PARTICIPANTS

A total of 6974 participants from the ELSA-Brasil study's second wave, aged 50 years and older, without overt thyroid dysfunction and with complete data for exposure, outcome, and covariates.

METHODS

Serum levels of thyrotropin (TSH), free thyroxine, and free triiodothyronine (FT3) were measured and divided in quintiles for the analyses. Participants were classified with euthyroidism, subclinical hypothyroidism, and subclinical hyperthyroidism. Muscle mass was assessed by bioelectrical impedance analysis and muscle strength by handgrip strength. Sarcopenia was defined according to the Foundation for the National Institutes of Health criteria. Possible confounders included sociodemographic characteristics, clinical conditions, and lifestyle. Analyses were performed separately for middle-aged and older adults (≥65 y).

RESULTS

The frequencies of sarcopenia, low muscle mass, low muscle strength, subclinical hypothyroidism, and subclinical hyperthyroidism were 1.5%, 20.8%, 3.8%, 9.1%, and .9%, respectively. Subclinical thyroid dysfunction was not associated with sarcopenia and its defining components. Among older adults, TSH had a U-shaped association with sarcopenia and low muscle strength. The odds ratios (ORs) (95% confidence intervals [CIs]) for the associations of the first, second, fourth, and fifth quintile with sarcopenia, respectively, were 5.18 (1.47-18.28), 6.28 (1.82-21.73), 4.12 (1.15-14.76), and 4.81 (1.35-17.10), and with low muscle strength was (OR (95% CI) for the first, second, and fifth quintiles, respectively: 1.43 (1.16-5.07), 2.07 (1.24-4.70), and 2.18 (1.03-4.60). Additionally, FT3 had a negative association with muscle mass in both age strata.

CONCLUSION

Subtle thyroid hormone alterations are associated with sarcopenia or its defining components in middle-aged and older adults without overt thyroid dysfunction. J Am Geriatr Soc 68:1545-1553, 2020.

A Significant Association of Upper Limb Muscle Strength with Thyroid Function in Overweight and Obese Population: A Study of the Sixth Korea National Health and Nutrition Examination Survey (KNHANES 2014-2015)

Background. As skeletal muscle is one of main targets of thyroid hormone signalling, an association of thyroid function and muscle strength could be expected. The aim of study is to evaluate the association of free thyroxine (FT4) and thyrotropin (TSH) with upper limb muscle strength, measured by hand grip strength, in subjects with normal FT4 from national representative data. The study utilized the sixth edition of the Korea National Health and Nutrition Examination Survey. After exclusion of subjects with FT4 level out of normal range, a history of thyroid disease or cerebral disease, restricted activity, and incomplete data, a total of 3503 were recruited (age range 19-80 years, 51% male). FT4 positively correlated with upper limb muscle strength (β coefficient = -12.84, p < 0.001), while TSH did negatively (β coefficient = -0.37, p=0.002). After adjusting for confounding factors, statistical significance disappeared. However, among subjects with BMI above 23 kg/m², a negative correlation of TSH with upper limb muscle strength was found in a younger age group (19-39 years old) (β coefficient = -0.56, p=0.021), while FT4 positively correlated with upper limb muscle strength (β coefficient = 3.24, p=0.019) in an older group (above 40 years old). In overweight and obese subjects, a significant association of thyroid function with upper limb muscle strength was observed in nation-wide representative data. High TSH in a younger group and low FT4 in an older group could be risk factors for decreased upper limb muscle strength in obese population.

Muscle Performance and Postural Stability Are Reduced in Patients with Newly Diagnosed Graves' Disease

Background: Reduced muscle strength is an acknowledged symptom of Graves' disease, but the knowledge on severity is sparse. This study aimed to investigate muscle strength, balance, and muscle function in patients with Graves' disease compared to age- and sex-matched healthy controls. Methods: Using a cross-sectional design, 55 patients newly diagnosed with Graves' disease were compared to 55 euthyroid controls, matched on sex, age, and menopausal status. Isometric muscle strength (N) and maximum force production (N/s) were measured across different muscles groups using a dynamometer chair and postural stability (balance) in different positions using a stadiometer. Muscle function was assessed using the Timed-Up-and-Go test and the Repeated Chair Stand test. Results: Patients and controls were well matched. Handgrip maximum muscle strength as well as strength at elbow and knee flexion and extension were significantly impaired in patients compared to controls. Maximum force production was only significantly reduced at elbow flexion. Patients performed the Timed-Up-and-Go and the Repeated Chair Stand test significantly slower than controls, and postural stability was significantly reduced in patients compared to controls in all positions. Free triiodothyronine correlated with reduced muscle strength and postural stability. Conclusions: At the time of diagnosis, Graves' disease is associated with impaired maximum muscle strength, performance, and balance, whereas maximum force production is overall comparable to euthyroid controls.

Association of Serum TSH With Handgrip Strength in Community-Dwelling Euthyroid Elderly

CONTEXT

Despite apparent muscle weakness in overt or even subclinical hyperthyroidism, the effects of thyroid function in the reference range on muscle strength are unknown.

OBJECTIVE

To investigate the association of serum TSH and free T4 with handgrip strength (HGS) in euthyroid elderly.

DESIGN AND SETTING

A nationally representative population-based, cross-sectional study from the Korea National Health and Nutrition Examination Surveys.

PARTICIPANTS

A total of 650 men aged ≥50 years and 533 postmenopausal women.

MAIN OUTCOME MEASURES

HGS was measured using a digital grip strength dynamometer, and low muscle strength was defined based on the Korean specific cutoff point of HGS (28.9 and 16.8 kg in men and women, respectively).

RESULTS

After adjustment for confounders, lower serum TSH but not free T4 was associated with lower HGS in men (P = 0.032). Compared with men with high-normal TSH, those with low-normal TSH consistently showed 5.0% lower HGS (P = 0.027), with a linear decrease in HGS across decreasing serum TSH quartiles (P for trend = 0.018). Men with low muscle strength had 22.0% lower serum TSH than those without (P = 0.015), and the odds for the risk of low muscle strength was 3.76 times higher among men with low-normal TSH than it was among those with high-normal TSH (P = 0.021). However, these associations were not observed in postmenopausal women.

CONCLUSIONS

These results suggest that serum TSH level at the lower end of reference range may be associated with low muscle strength, especially in older men.

Bio-energetic impairment in human calf muscle in thyroid disorders: a 31P MRS study

Mitochondrial metabolism particularly oxidative phosphorylation is greatly influenced by thyroid hormones. Earlier studies have described neuromuscular symptoms as well as impaired muscle metabolism in hypothyroid and hyperthyroid patients. In this study, we intend to look in to the muscle bioenergetics including phosphocreatine recovery kinetics based oxidative metabolism in thyroid dysfunction using in vivo (31)P nuclear magnetic resonance spectroscopy (MRS). (31)P MRS was carried out at resting state on 32 hypothyroid, 10 hyperthyroid patients and 25 control subjects. Nine out of 32 hypothyroid patients and 17 out of 25 control subjects under went exercise protocol for oxidative metabolism study and performed plantar flexion exercise while lying supine in 1.5 T magnetic resonance scanner using custom built exercise device. MRS measurements of inorganic phosphate (Pi), phosphocreatine (PCr), phosphodiesters (PDE) and adenosine triphosphate (ATP) of the calf muscle were acquired during rest, exercise and recovery phase. PCr recovery rate constant (k(PCr)) and oxidative capacity were calculated by monoexponential fit of PCr versus time (t) at the beginning of recovery. During resting condition in hypothyroid patients, PCr/Pi ratio was reduced whereas PDE/ATP and Pi/ATP were increased. However, in case of hyperthyroidism, an increased PCr/Pi ratio and reduced PDE/ATP and Pi/ATP were observed. The results confirmed differential energy status of the muscle due to increased or decreased levels of thyroid hormone. Our results also demonstrate reduced oxidative metabolism in hypothyroid patients based on PCr recovery kinetics. PCr recovery kinetics study after exercise revealed decreased PCr recovery rate constant (k(PCr)) in hypothyroid patients compared to controls that resulted in decrease in oxidative capacity of muscle by 50% in hypothyroids. These findings are consistent with a defect of high energy phosphate mitochondrial metabolism in thyroid dysfunction.

Changes in body composition in women following treatment of overt and subclinical hyperthyroidism

OBJECTIVE

To determine changes in weight, body composition, and bone density after treatment of overt hyperthyroidism (OH) and subclinical hyperthyroidism (SCH) in women.

METHODS

Women with OH and SCH referred to the Mayo Clinic Thyroid Clinic were recruited. Hyperthyroid patients and euthyroid control women were matched for age (within decade) and body mass index. Patients with OH and SCH were treated to normalize thyroid function test results and were restudied after 6 months of normal thyroid function. Baseline and posttreatment studies included measurement of height, weight, bone density, lean mass, fat mass, and thigh muscle cross-sectional area. All participants had normal thyroid function test results for at least 6 months before completion of the posttreatment studies.

RESULTS

Twenty-four patients with OH, 21 patients with SCH, and 36 control patients were studied. In the OH group, fat-free mass increased from a mean of 36.8 kg (95% confidence interval [CI], 34.8-38.8) to 40.4 kg (95% CI, 38.5-42.3); in the SCH group, fat-free mass increased from a mean of 40.3 kg (95% CI, 38.1-42.5) to 42.2 kg (95% CI, 39.7-44.7). In both groups, fat mass increased to approximately the same extent, and both groups experienced significant weight gain with no change in percent body fat. Thigh muscle cross-sectional area increased in both groups -- from 100.6 cm(2) (95% CI, 92.7-108.5) to 113.3 cm(2) (95% CI, 105.5-121.1) in the OH group and from 106.1 cm(2) (95% CI, 96.7-115.5) to 112.2 cm(2) (95% CI, 102.0-122.4) in the SCH group. Bone density increased in patients with OH (P<.01) and in patients with SCH (P<.05).

CONCLUSIONS

Treatment of OH and SCH leads to increases in muscle area and bone density. Weight gain reflects increases in both fat and fat-free mass. While these results provide some support for actively treating SCH in women, further prospective studies are needed to determine whether the changes documented translate into real patient benefit.

Thigh muscle stiffness assessed with magnetic resonance elastography in hyperthyroid patients before and after medical treatment

PURPOSE

To measure the stiffness of the vastus medialis (VM) in hyperthyroid patients before and after treatment.

MATERIALS AND METHODS

A total of five healthy euthyroid patients and five hyperthyroid patients were tested using magnetic resonance elastography (MRE), which involves the induction of shear waves in the thigh muscles using a pneumatic driver at 90 Hz.

RESULTS

Among the pretreatment hyperthyroid cohort a lower stiffness was found when the muscle was relaxed (2.11 +/- 0.61 kPa) compared the stiffness following treatment of hyperthyroidism (5.52 +/- 1.52 kPa), which was accompanied by an improvement in the contractile function of the VM. Pretreatment muscle stiffness was also less than that of age matched healthy volunteers (4.56 +/- 0.40 kPa). The behavior of the waves was sensitive to the stage of this myopathy and to the amount of free thyroxine (FT4).

CONCLUSION

The MRE technique provides a new tool to gain new insights into pathophysiology of thyroid associated and other muscle diseases and their response to treatment.

Resistance Training Improves Muscle Function and Body Composition in Patients With Hyperthyroidism

OBJECTIVE

To evaluate the effect of resistance training on skeletal muscle performance and body composition in patients with medically treated hyperthyroidism.

DESIGN

Nonrandomized controlled trial.

SETTING

Large public tertiary hospital.

PARTICIPANTS

Sixteen sedentary patients with recent clinical diagnosis and laboratory confirmation of hyperthyroidism (7 men, 9 women; age, 38+/-11 y; weight, 58.4+/-2.6 kg; height, 1.6+/-0.3m) were assigned to the control group (medical therapy; n=9) or training group (medical therapy associated with resistance training; n=7). An age- and sex-matched healthy group served as controls (3 men, 5 women; age, 40+/-3 y; weight, 68.4+/-4.3 kg; height, 1.6+/-0.3m).

INTERVENTION

Resistance training twice a week for 16 weeks.

MAIN OUTCOME MEASURES

Peak muscular strength (by dynamometry and 1 repetition maximum method) and endurance (30% of peak force) for 7 movements and anthropometric measurements.

RESULTS

The hyperthyroid patients as a group had lower baseline overall strength values when compared with healthy subjects (200.3+/-16.0 kg vs 274.9+/-21.8 kg, respectively; P=.006). Overall absolute increases in strength (49 kg vs 91 kg, P<.05) and endurance (78.5x10(2)kg/s vs 176.9x10(2)kg/s, P<.05) were higher in the training group compared with the control group. Body weight increased in both groups, but the sum of muscular circumference increased only in the training group (training group, 92.6+/-3.3 cm vs 97.1+/-3.8 cm; control group, 94.6+/-2.2 cm vs 94.4+/-2.1cm; P<.05), with no change in the sum of skinfolds.

CONCLUSIONS

Resistance training accelerates the recovery of skeletal muscle function and promotes weight gain based on muscle mass improvement in patients with medically treated hyperthyroidism.

The impact of overt and subclinical hyperthyroidism on skeletal muscle

OBJECTIVE

Patients with overt hyperthyroidism (OH) commonly have proximal limb muscle weakness that improves after correction of hyperthyroidism. It is unclear, however, if patients with milder degrees of hyperthyroidism (referred to as subclinical hyperthyroidism or SCH) may also have a degree of muscle weakness. This may have clinical relevance as SCH patients are often elderly and may therefore have concurrent sarcopenia of aging and would represent a previously unrecognized complication of SCH.

DESIGN

We measured both thigh strength and cross-sectional area in patients with OH (n = 30) or SCH (n = 24), both prior to treatment of hyperthyroidism and again at 6-9 months after the restoration of a euthyroid state. Euthyroid controls (n = 48) were studied at similar time intervals.

MAIN OUTCOME

Prior to treatment, both knee flexor and extensor muscle strength was reduced in both patients with OH and SCH compared to controls (p < 0.05). After treatment all strength measurements improved in the OH group (p < 0.01) while in the SCH group the majority of muscle strength measurements improved (p < 0.05). Midthigh muscle cross-sectional area was reduced in both the OH and SCH group at baseline (p < 0.05) compared to controls and increased significantly following treatment (p < 0.05). There were no significant changes in any parameter in the euthyroid control (EC) group during the study period.

CONCLUSIONS

The finding that muscle strength and cross-sectional area are reduced in SCH and improved after treatment lends support for the clinical decision to treat rather than observe this condition. This may have particular relevance to certain SCH patient groups including the elderly who are prone to falls and athletically active younger patients who require optimal skeletal muscle function.

Disfunção muscular esquelética e composição corporal no hipertireoidismo

O objetivo deste artigo é revisar os aspectos da disfunção muscular esquelética e composição corporal no hipertireoidismo. O hipertireoidismo está associado a uma fraqueza muscular generalizada que é parte da manifestação clínica inicial de cerca de 80% dos pacientes, comprometendo a realização de tarefas cotidianas e a qualidade de vida. Um fator que contribui para a redução da força é a atrofia muscular, que tende a afetar mais comumente os grupos musculares proximais. Além disso, o hipertireoidismo é acompanhado de perda ponderal associada à depleção de massa muscular e tecido adiposo. Estudos demonstram que o tratamento medicamentoso é capaz de recuperar a força e mais lentamente a resistência, definida como a capacidade de sustentar cargas submáximas por períodos prolongados, e que o treinamento contra resistência associado ao tratamento medicamentoso, é capaz de promover um maior ganho de força e de resistência muscular nestes pacientes. Embora não tenha sido estabelecido um padrão de composição corporal na recuperação do peso após o tratamento da doença, sabe-se que pacientes submetidos ao treinamento de força apresentam recuperação de peso acompanhado principalmente de ganho de massa muscular.

Função muscular esquelética e composição corporal de pacientes com hipertireoidismo submetidos ao treinamento contra resistência

O hipertireoidismo está associado a uma fraqueza muscular generalizada que é parte da manifestação clínica inicial de cerca de 80% dos pacientes. A recuperação da performance muscular esquelética durante o tratamento do hipertireoidismo depende tanto do aumento da massa muscular quanto da melhoria da função intrínseca da musculatura esquelética. Por outro lado, o treinamento contra resistência aumenta a força e a endurance muscular em diferentes grupos de indivíduos. O objetivo do presente trabalho foi avaliar o efeito deste tipo de treinamento sobre a recuperação da função muscular esquelética de pacientes portadores de hipertireoidismo. Os pacientes, atendidos no ambulatório de endocrinologia, diagnosticados clínica e laboratorialmente com doença de Graves, foram submetidos, antes do tratamento e quatro meses após, a medidas antropométricas e testes de força máxima e endurance musculares (sustentando 30% da carga máxima) de quatro movimentos [handgrip esquerdo (HE) e direito (HD), legpress (LEG), flexão plantar de tornozelo (FPT) e supino reto (SR)]. Após a avaliação inicial, os pacientes foram divididos em dois grupos: 1) controle (GC - tratamento medicamentoso) e 2) treinamento (GT - acrescentado treinamento contra resistência individualizado 2X/semana). Os resultados (GC, n = 3; GT, n = 4; todas do sexo feminino) mostram: <img src="/img/revistas/rbme/v7n1/a04tab01.gif"> Os autores concluem que o treinamento contra resistência parece favorecer aumento da massa e da performance muscular esquelética em pacientes com hipertireoidismo.

Skeletal muscle function and body composition of patients with hyperthyroidism

The purpose of this study was to determine whether the improvement in muscle performance after treatment of hyperthyroidism is only a result of an increased muscle mass or if it also depends on the improvement of intrinsic contractile function. Nine patients with Graves' disease were evaluated 1) at the time of diagnosis, 2) after 1 wk of monotherapy with propranolol, and 3) after the euthyroid state had been achieved with antithyroid drugs. At each evaluation the patients were submitted, on the dominant side, to anthropometric measurements and to skeletal muscle function tests to determine the maximal static voluntary contraction (MAX) and endurance (END); "endurance" is defined as the time limit at maintaining 30% of MAX. Three movements were tested: hip flexion, ankle dorsiflexion, and handgrip. Body weight changed from 53.4 +/- 3.2 to 58.2 +/- 2.9 kg (P = 0.004) and the sum of skinfold-corrected limb circumferences changed from 90.7 +/- 3.1 to 94.4 +/- 3.1 cm (P = 0.017). MAX and END of all movements increased at the end of the study even if adjusted for the sum of skinfold-corrected limb circumferences: Hip flexion: MAX 20.60 +/- 3.32 to 31.26 +/- 5.07 g.cm-1, END 0.43 +/- 0.18 to 1.18 +/- 0.42 kg.s-1.cm-1. Ankle dorsiflexion: MAX 12.34 +/- 1.97 to 26.88 +/- 2.46 g.cm-1, END 0.97 +/- 0.28 to 2.50 +/- 0.58 kg.s-1.cm-1; Handgrip: MAX: 2.20 +/- 0.23 to 2.9 +/- 0.2 g.cm-1, END 0.13 +/- 0.01 to 0.20 +/- 0.02 kg.s-1.cm-1. In conclusion, improved muscle performance resulting from the treatment of hyperthyroidism is a consequence of an enhanced intrinsic muscle function as well as a greater muscle mass.