Original article / research
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Spirometric Evaluation of Pulmonary Expiratory Flow Volume and Flow Rate in Patients with Clinical Hypothyroidism at a Tertiary Care Hospital, West Bengal, India: A Case-control Study |
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Mainak Ghosh, Bosumita Sinha, Joyashree Banerjee, Bulbul Mukhopadhyay 1. Assistant Professor, Department of Physiology, Murshidabad Medical College and Hospital, Berhampur, West Bengal, India. 2. Associate Professor, Department of Physiology, RG Kar Medical College, Kolkata, West Bengal, India. 3. Associate Professor, Department of Physiology, RG Kar Medical College, Kolkata, West Bengal, India. 4. Professor and Head, Department of Physiology, RG Kar Medical College, Kolkata, West Bengal, India. |
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| Correspondence
Address : Joyashree Banerjee, Flat No. C/8, Government Housing Estate, 82-Belgachia Road , Kolkata-37, West Bengal, India. E-mail: banerjeedrjoyashree@gmail.com |
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| ABSTRACT |  | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| : Hypothyroidism is defined as a clinical condition caused by insufficient thyroid hormone secretion from the thyroid gland as a result of structural or functional defects in thyroid hormone production. Hypothyroidism can impair respiratory function and cause ventilation problems. Spirometry is used to assess pulmonary function in patients with thyroid disorders because low thyroid hormone levels can cause bronchial hyperactivity and obstructive pulmonary disease. Aim: To find out the changes of spirometric parameters in clinical hypothyroid patients compared to apparently healthy individuals. Materials and Methods: The study was a case-control study conducted in the Department of Physiology of Burdwan Medical College and Hospital on 50 cases and 50 apparently healthy subjects. Inclusion criteria were diagnosed cases of clinical hypothyroidism, Body Mass Index (BMI) under 30 kg/m2, and age between 20 to 50 years. Serum TSH and free T4 (FT4) were measured by Quantitative EIA method using RFCL-manufactured commercial “ELISCAN-TSH”-kitand“ELISCAN-Ft4”-kit. Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 second (FEV1), FEV1/FVC, Forced Expiratory Flow (FEF) of 25-75%, and Peak Expiratory Flow Rate (PEFR) parameters of pulmonary function test were tested by RMS Helios 401 Spirometer. Pearson’s two-tailed correlation study and student independent-test were done for analysis. Results: The present study showed that spirometric parameters FEV1, FVC, FEV1/FVC, PEFR and FEF25%-75% were significantly decreased in clinical hypothyroidism compared to control. Mean values of parameters of FEV1, FVC, FEV1/FVC, PEFR and FEF25%-75% in clinical hypothyroid cases were 85.30%, 92.42%, 90.70%, 74.86%, and 75.63%, respectively which were significantly (p<0.001) decreased compared to that of healthy individuals. Conclusion: This study concluded that clinical hypothyroidism causes significant changes in respiratory function. Thus, a proper knowledge in respect to this infection would help in management of these patients in time. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Keywords : Forced vital capacity, Lung function, Spirometer, Thyroid | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| INTRODUCTION | | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Anatomist Andreas Vesalius gave the anatomic description and illustration of the thyroid gland in 1953 (1). The gland was named thyroid by the anatomist Thomas Wharton in 1656 (2), Thomas Curling first described hypothyroidism in 1850 (3). All organ systems are affected by hypothyroidism [4,5]. The clinical manifestation of thyroid hormone deficiency differs from person to person depending on the degree of deficiency, cause, and duration. Diaphragmatic dysfunction may be experienced by the patients of hypothyroidism that can range from mild forms having decreased tolerance to physical effort to severe forms of diaphragmatic weakness that may mimic diaphragmatic paralysis (6). In hypothyroid patients, the respiratory rate is reduced, resulting in hypoventilation and mild hypercapnia (7),(8). Hypercapnia stimulates the respiratory centre, which is unable to respond to an increased need for ventilation due to low thyroid hormone levels. Birring SS discovered that patients with low thyroid hormone levels, the cough reflex is more sensitive, and the airways are more responsive (9). Obstructive sleep apnoea is a common symptom of hypothyroidism. Studies evaluating the static (vital capacity, tidal volume, inspiratory reserve volume, expiratory reserve volume, inspiratory capacity, total lung capacity) and dynamic parameters of pulmonary function (FVC, FEV1, PEFR, FEF 25-75%) with spirometry are inconsistent regarding whether thyroid disorders are leading to lung dysfunction. In hypothyroid patients, there is decrease in vital capacity values, while FVC and FEV were inconsistently lowered (10),(11),(12). Several studies have found that patients with clinical hypothyroidism have a significant decrease in the strength of their inspiratory and expiratory muscles (13),(14),(15). Therefore, there may be respiratory dysfunction in clinical hypothyroidism (16). Very few studies are there regarding this, only one study (17) on spirometric assessment of lung function in eastern zone of India. On this background the present study was conducted to assess the presence of any respiratory dysfunction in clinical hypothyroid patients. This study was conducted with an intent to enlighten the alteration of function of lung, if any by spirometry in patients of clinical hypothyroidism in a semi-urban population of Burdwan district and neighbouring areas of West Bengal, a part of Eastern India. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| MATERIAL AND METHODS | | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| This case-control study was conducted in the Physiology Department of Burdwan Medical College & Hospital, West Bengal, India for a period of one year from February 2010 to January 2011. Clearance certificate from IEC was obtained (Certificate no-BMC/PG/167(56) Dated 14th January. Patients and healthy volunteers both provided informed written consent. Inclusion criteria: Subjects with clinical hypothyroidism, aged between 20 to 50 years with BMI under 30 kg/m2 were taken as cases. Age and sex matched healthy subjects were selected as control. Exclusion criteria: Smoking history and any other respiratory and systemic disease that affect respiratory system were excluded from our study. Sample size calculation: The formula used for calculating the adequate sample size (18) was n=Z2P(1-P)/d2.Where n was the sample size, Z was the statistic corresponding to level of confidence, P was expected prevalence, and d was precision (corresponding to effect size), Confidence Interval (CI), Z=1.96, CI=95%, P=10.95% (19), d(absolute precision)=0.05 Thus, n=150 (approx.) Study Procedure Fifty clinical hypothyroid patients along with 50 apparently healthy subjects were considered for the study based on the laboratory values of TSH and fT4. Clinical features of hypothyroidism range from no symptoms to life-threatening symptoms [20-22]. Clinical hypothyroidism is defined as an elevated TSH level (> 6.16 μIU/mL) with a decreased serum fT4 levels (<0.8 ng/dL) [20,23]. The term hypothyroidism was defined using reference ranges for the relevant biochemical parameters; normal TSH level (0.39-6.16 μIU/mL) and normal serum fT4 levels (0.8-2.0 ng/dL) (23). Apparently healthy individuals were considered as comparative normal group. Study parameters: (i) Estimation of serum TSH: by ‘Quantitative EIA method’ using RFCL-manufactured commercial “ELISCAN-TSH”- kit (24). (ii) Estimation of serum free T4: by ‘Quantitative EIA method’ using RFCL-manufactured commercial “ELISCAN-fT4”- kit (25). (iii) Assessment of spirometric parameters like FVC, FVC%, FEV1, FEV1%, FEV1/FVC, FEF25-75%, PEFR, PEFR% by RMS Helios 401 Spirometer. The thyroid function of all the subjects was rechecked in biochemistry laboratory to confirm their TSH and fT4 status. Then, history was recorded for all the study subjects and they were clinically evaluated with a thorough general survey and systemic examination. Respiratory system examination was done meticulously. Demonstration was given about the technique of FVC to all study subjects after taking rest for 10 minutes. Then spirometry was carried out in a room with privacy, in a sitting posture closing the nostrils with a nose clip. An average of three readings was taken. Spirometry necessitates a voluntary manoeuvre in which patient in sitting postures inhales maximally from tidal respiration to total lung capacity then exhales rapidly to the greatest extent possible until no more volume is exhaled at residual volume. The manoeuvre was carried out forcefully in order to generate a FVC. Statistical Analysis It was done using SPSS software version 17 and Microsoft Excel software of MS-office 2007 software package in computer. Pearson’s two tailed correlation study and student independent t-test were done for analysis. The p-values were calculated to deduce the significance level and p-value <0.05 has been considered statistically significant. To assess the relationship between TSH and respiratory parameters and fT4 and respiratory parameters, Pearson’s correlation test was used for finding the correlation. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| RESULTS | | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| In this study, 50 clinical hypothyroidism patients with BMI under 30 kg/m2 were selected. Among all the 50 subjects 78% were females and 22% were males. The mean ages of the clinical hypothyroidism and the control group of subjects were 38.60±5.05 years, 36.78±4.62 years respectively (Table/Fig 1). There were no significant differences in ages between cases and control. There the mean fT4 and TSH values were significantly (p<0.001) different between the cases and the controls (Table/Fig 2). (Table/Fig 3) shows the comparison between spirometric values of the clinical hypothyroidism and control groups of patients. It showed that in the control group all the spirometric parameters were significantly (p≤0.05) higher than that of the clinical hypothyroidism patients. (Table/Fig 4),(Table/Fig 5),(Table/Fig 6) shows correlation between TSH value and spirometric parameters of clinical hypothyroidism patients. It is clear that only FEF25-75 (L) and PEFR (L) had highly significant (p<0.01) negative correlation with TSH values (r=-0.462, p=0.002 and r=-0.396, p=0.009, respectively). The other spirometric parameters do not have statistically significant correlation (p<0.05) with TSH value. The [Table/Fig-7-10] shows that statistically significant positive correlation is present between FT4 and FEF25-75 (L) (r=0.457, p=0.002), between FT4 & PEFR (L) (r=0.437, p=0.003). Significant negative correlation persists between FT4 & FEV1/FVC (r=-0.367, p=0.015). But no significant association was there between FT4 and other spirometric parameters. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| DISCUSSION | | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| The impairment of pulmonary function in hypothyroidism is caused by both central and peripheral factors. Thyroid hormone deficiency centrally suppresses hypoxic and hypercapnic ventilatory drives. Low thyroid hormone causes peripheral myopathy with decreased respiratory muscle strength. Hypothyroidism causes hypoventilation as ventilatory response to hypoxia and hypercapnia is reduced in hypothyroidism (26). Hypothyroidism is characterised by diminished expiratory and inspiratory muscle strength (27). In this study, in the control group all spirometric parameters were higher than that of the in the clinical hypothyroidism patients. Low FVC% in the hypothyroid group indicated a restrictive pattern of pulmonary impairment. A study by Cakmak G et al., reported reduced FVC, FVC%, and FEV1 in hypothyroid patients which were similar to the findings with the present study (28). Maiti SR et al., found a significant reduction in FVC, FEV1, and FEV1/FVC in hypothyroidism (17). Sharon R et al., also found that both of FVC% and FEV1/FVC were significantly reduced whereas Sadek SH et al., showed that in hypothyroidism patients FVC% was reduced. These studies corroborated with the present study [29,30]. Sadek SH et al., and Valjevac S et al., also found that hypothyroidism was associated with decreased FEV1, FVC and total lung capacity (30),(31). In present study, a significant negative correlation of TSH with FEF25-75(L) and PEFR (L) was found. A positive correlation of fT4 with FEF25-75 (L) and PEFR (L) was also observed in this study. Cakmak G et al., found that FVC% was significantly negatively associated with TSH whereas FVC%, and FEF25-75, FEF25-75%, PEFR, % PEFR were significantly positively correlated with FT3 in clinical hypothyroidism patients (28). However, in euthyroid subjects they found no significant correlation between thyroid hormones and parameters of lung function. Similar findings were showed by Maiti SR et al., and Valjevac S et al., (17),(31). They reported that TSH and FVC were positively associated in hypothyroidism patients. However, Roel S et al., found no significant correlation between TSH and fT4 and spirometric parameters. Lower thyroid hormone levels and higher TSH levels indicated more severe hypothyroidism, which resulted in a greater decrease in spirometric parameters. (Table/Fig 11) contains a comparison of similar studies from the literature (17),(26),(27),(28),(29),(30),(31). Limitation(s) FT3 value could not be measured due to lack of facility in our institution and the sample size was less than the estimated size. The study will be better evaluated in future with considering these limitations. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| CONCLUSION | | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| The current study found a statistically significant difference in FVC, FEV1, FEV1/FVC, PEFR% and FEF 25-75 in the clinical hypothyroidism patients compared to apparently healthy controls. Therefore, pulmonary function test must be done in all the patients diagnosed as hypothyroidism. A convenient, cost-effective and non invasive simple spirometry may help in early detection of abnormal lung function in clinical hypothyroidism and thus plays an important role in early initiation of treatment which may prevent serious respiratory problems. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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