Evaluation of lung function by spirometric parameters and its association with serum TCH and serum fT4 in subclinical hypothyroidism in a tertiary care hospital serving rural population in West Bengal

Introduction: Subclinical hypothyroidism is described as a condition where the patients™ serum ft4 is within normal limit , but serum TSH level is raised . These patients have limited or no clinical features of hypothyroidism. It is to be mentioned here that clinical hypothyroidism is biochemically denoted as an elevated TSH level with a decreased serum fT4 level along with florid symptoms of hypothyroidism. There are numerous researches on how clinical hypothyroidism affects the respiratory system, but there are scanty numbers relating to subclinical hypothyroidism, which may also lead to remarkable deficits in lung function. Evaluation of the respiratory system in subclinical hypothyroidism is the prime target of this study . Spirometry was our method of choice here since it is less expensive, smoother, and more readily available than other respiratory function tests.
Aims and Objective: To measure the Expiratory Flow Volumes – FEV1, FVC, FEV1%, FVC%, FEV1:FVC% and rates- PEFR(L), PEFR%, \(FEF_{25-75}\) (L), \(FEF_{25-75}\) %, in subclinical hypothyroid patients and their correlation with serum TSH level and serum fT4 level.
Materials and Methods: The current study was a cross-sectional study with a case-control design conducted at the physiology department of a tertiary hospital situated in West Bengal surrounded by rural population. The selection of 100 subjects (50 cases and 50 controls) was based on age, BMI, inclusion and exclusion criteria. Serum TSH and fT4 levels were measured, and the pulmonary function tests were examined using the RMS Helios 401 Spirometer. The statistical study was conducted using Microsoft Office 2007’s SPSS-17 and Excel. The Student Independent T-test and the Pearson’s Two-Tailed Correlation Study were used for the analysis. The threshold for statistical significance was a P value of \(\leq 0.05\) and P value \(\leq 0.001\) was considered as statistically highly significant.
Results: The pulmonary function parameters in active control subjects and in subclinical hypothyroidism patients were measured by spirometry . It was noticed all the projected study parameters of pulmonary function test were lowered considerably in subclinical hypothyroidism in respect with the control group. The dissimilarities of the FVC, FVC%, FEV1, FEV1%, PEFR(L), PEFR%, FEV1/FVC, \(FEF_{25-75}\) (L) are statistically important (\(p \leq 0.05\)). In SCH , significant negative correlation persists between TSH and FVC(L), between TSH and FEV1(L) and between TSH and FEV1%. In SCH patients, FVC(L) , FVC%, FEV1% and PEFR(L) have significant correlation with fT4 value.
Conclusions: The present study depicts that subclinical hypothyroidism also may cause disorders of lung function along with disturbances of ventilation. Simple spirometry may be used to test patients for the widely prevalent subclinical hypothyroidism affecting a good number of common people. This will aid in prompt patient management.