title: Prevalence of diaphragmatic muscle weakness and dyspnoea in Graves' disease and their reversibility with carbimazole therapy.
abstract: OBJECTIVE
  Dyspnoea is a common complaint among patients with thyrotoxicosis. However, its causative mechanisms have not been identified. We assessed the role of thoracic diaphragmatic muscle weakness in dyspnoea among patients with active Graves' disease.
  
  
  METHODS
  Twenty-seven patients (19 female, 8 male) with active Graves' disease were assessed for the clinical severity of dyspnoea, functional (pressure generating capacity) and anatomical aspects (thickness and excursion) of the diaphragm at presentation. The severity of dyspnoea was assessed using a visual analogue scale (VAS) and the 6 min walk test. Lung function tests, diaphragmatic strength (sniff oesophageal pressure, SniffP(oeso)), maximum inspiratory and expiratory pressures, diaphragmatic thickness and movements on real time ultrasonography were evaluated during normal and deep respiration. Twenty of the 27 patients were reassessed after achieving euthyroidism with carbimazole therapy at a mean interval of 5+/-2 months.
  
  
  RESULTS
  Reevaluation after carbimazole therapy revealed a significant reduction in dyspnoea on the VAS (59+/-26 to 23+/-13%). Patients covered a similar distance during the 6 min walk before and after euthyroidism. Significant improvement was observed in the vital capacity (2.57+/-0.62 to 2.94+/-0.60 l), forced expiratory volume in the first second (2.21+/-0.49 to 2.45+/-0.47 l), total lung capacity (3.57+/-1.19 to 4.1+/-1.12 l), diaphragmatic movement during deep respiration (5.5+/-1.0 to 6.6+/-1.1 cm) and SniffP(oeso) (68.7+/-23 to 93.1+/-25.2 cmH(2)O). There was no significant change in the distance walked in 6 min, tidal volume, lung diffusion capacity and diaphragmatic thickness. There was no significant correlation between the net change in dyspnoea score and net change in lung function tests, diaphragmatic movement and SniffP(oeso).
  
  
  CONCLUSIONS
  Significant functional weakness of diaphragm muscle is present in patients with active Graves' disease. This weakness is more marked during a maximal respiratory manoeuvre, indicating a diminished diaphragmatic reserve which could be the cause of dyspnoea observed on exertion among patients with thyrotoxicosis.
authors.affiliation: Department of Endocrinology, All India Institute of Medical Sciences, New Delhi 110029, India. gosravinder@hotmail.com
authors.forename: Ravinder
authors.initials: R
authors.lastname: Goswami
authors.forename: Randeep
authors.initials: R
authors.lastname: Guleria
authors.forename: Arun Kumar
authors.initials: AK
authors.lastname: Gupta
authors.forename: Nandita
authors.initials: N
authors.lastname: Gupta
authors.forename: Raman Kumar
authors.initials: RK
authors.lastname: Marwaha
authors.forename: Jitender Nath
authors.initials: JN
authors.lastname: Pande
authors.forename: Narayana
authors.initials: N
authors.lastname: Kochupillai
mesh_terms: D000328:Adult; D013956:Antithyroid Agents / Q000627:therapeutic use*; D002231:Carbimazole / Q000627:therapeutic use*; D003964:Diaphragm / Q000503:physiopathology; D004417:Dyspnea / Q000453:epidemiology / Q000209:etiology*; D015444:Exercise; D005260:Female; D005541:Forced Expiratory Volume; D006111:Graves Disease / Q000150:complications* / Q000188:drug therapy; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000453:epidemiology / Q000209:etiology*; D012129:Respiratory Function Tests; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014797:Vital Capacity
chemical_list: D013956:Antithyroid Agents; D014284:Triiodothyronine; D002231:Carbimazole; D013974:Thyroxine