Status of Thyroid Function among Patients of National Medical College and Teaching Hospital

MED PHOENIX: An Official Journal of NMC, Birgunj, Nepal Volume (5), Issue (1), July 2020, 64-70 ABSTRACT Background: Thyroid dysfunction is one of the most common endocrinopathies after Diabetes Mellitus. Thyroid dysfunction is defined as the alteration in Thyroid Stimulating Hormone (TSH) with normal or abnormal thyroid hormones. Nepalese population have a high risk for thyroid dysfunction with a high prevalence of iodine deficiency.


INTRODUCTION
Thyroid dysfunction is one of the most common endocrinopathies after Diabetes Mellitus. 1 Thyroid dysfunction is defined as the alteration in Thyroid Stimulating Hormone(TSH) with normal or abnormal thyroid hormones (triiodothyronine and tetraiodothyronine). 2 With decreased or increased thyroid hormones in the blood, thyroid dysfunction is categorized as hypothyroidism or hyperthyroidism, respectively. In case of subclinical thyroid dysfunction where the level of thyroid hormones is normal, the level of TSH determines the nature of thyroid dysfunction. Serum TSH with free or total thyroid hormones is commonly used to screen and monitor thyroid disorders. The American Thyroid Association recommends that adults be screened for thyroid dysfunction by measurement of the serum thyrotropin concentration, beginning at age 35 years and every 5 years there after. 2,3 Globally thyroid dysfunction affects about 300 million people and more than half are supposed to be unaware of their condition. 4 There is no such study to our knowledge that documents prevalence of thyroid disorder of Nepal. However, several studies showed the prevalence of thyroid dysfunction in various region of Nepal. The prevalence of thyroid disorder was 30% in eastern Nepal (Baral N et al.,2002 ) and 17.42% in western Nepal (Risal P et al. 2010). 5,6 Prevalence of thyroid dysfunction in the central and far-western region was 29% and 33.6% respectively. 7,8 Nepalese population have a high risk for thyroid dysfunction with a high prevalence of iodine deficiency. 9 Apart from iodine deficiency, several factors are responsible for exacerbating the thyroid dysfunction in the context of Nepal. 2 The study conducted for 3 years by Gupta RK et al. (2009to 2012 at National Medical College, Birgunj, Nepal showed the prevalence of overt and subclinical hyperthyroidism. 10 As best to our knowledge there are no such epidemiological records that depict the overall status of thyroid dysfunction in National Medical College, Birgunj, Nepal. This study aims to document the prevalence of thyroid dysfunction in populations of Province Two, visiting National Medical College and Teaching Hospital, Birgunj, Nepal.

Data collection:
The study was carried out using data retrieved from the register maintained in the Central Laboratory Services (CLS) of the National Medical College and Teaching Hospital, Birgunj between July 2017 to December 2019. Over this period, a total of 7040 patients underwent assessment of thyroid function. The variables collected were age, sex, and thyroid function profile including free triiodothyronine (fT3), free tetraiodothyronine (fT4) and Thyroid Stimulating Hormone (TSH). The study was approved by an Institutional Review Committee (IRC) of National Medical College and Teaching Hospital, Birgunj, Nepal.
Collection of blood samples: Venous blood sample (2-3 ml) was collected from the antecubital vein in a plain vial, and was allowed to clot, then subsequently serum was separated by centrifugation at 3000g for 10 minutes and thyroid function test was performed. Samples which were not possible to process within regular lab hours were stored at 4°C until TSH and free thyroid hormones were estimated.

Assay procedure for thyroid hormones:
Thyroid hormones (fT3 and fT4) and TSH were estimated by Chemiluminescence Immunoassay(CLIA) method using Access 2 Beckman Coulter analyser. (Beckman Coulter Inc., California, USA). The reference ranges for TSH, fT4 and fT3 were 0.34 -5.6 µIU/mL, 6.1-11.2pg/mL and 2.5 -3.9pg/mL, respectively. Individuals who had all three hormones within the reference range were considered euthyroid. Study groups with abnormal thyroid functions were further categorized as subclinical hypothyroidism (normal fT4 and fT3 with increased TSH), overt hypothyroidism(decreased fT4 and fT3 with increased TSH), subclinical hyperthyroidism(normalfT4 and fT3 with decreased TSH) and overt hyperthyroidism(increased fT4 and fT3 with decreased TSH) 11,12

STATISTICAL ANALYSIS
The data entered in MS Excel 2010 and analyzed by Statistical Package for Social Science (SPSS) version 16.0 (SPCC Inc. Chicago). Descriptive and inferential statistics were applied. Data were presented as frequency, percentage and mean ±SE. The ANOVA test was applied to check the significant difference of variables between each group. P-value <0.05(at 95% confidence interval was considered statistically significant.

Figure 1: Status of thyroid functions in the study group
In this study total of 7040 individuals underwent for assessment of thyroid function. Figure 1 13,14,15 Large group of population is found to have hypothyroidism compared to other thyroid disorder. 16,17 Iodine deficiency may be one of the major cause of hypothyroidism in the Nepalese population as mentioned in various studies. 16 Our study showed total hypothyroidism(subclinical and overt) in 22.3% of females and 18.99% of males. Hypothyroidism and hyperthyroidism are more common in females than in males. 17 The reason may be due to hormonal change, such as during or after pregnancy or after menopause. Sex hormones, especially estrogen and prolactin, have an important role in modulating the immune system and may impact autoimmune disease. Hashimoto's thyroiditis is another major cause of hypothyroidism which is more common in females. 18 Hyperthyroidism was reported in 9. In this study mean±SE for TSH, fT4 and fT3 levels show statistically significant differences in different thyroid disorders. Similar results were obtained by Yadav NK et al. 8 and Mahato RV et al. 7 In another study by Aryal M et al. 2 , fT3 and TSH were significantly different in various groups of thyroid dysfunction but free T4 level was statistically insignificant.

CONCLUSION
The study documented a high prevalence of subclinical hypothyroidism followed by overt hypothyroidism among the patients visiting National Medical College and Teaching Hospital, Birgunj, Nepal. Best to our knowledge this is the first study to record the prevalence of all forms of thyroid dysfunction of the population in province 2. However, it is a hospital-based study and therefore does not represent the epidemiological study of an entire province. The study recommends proper screening, treatment and finding the etiology of all forms of thyroid dysfunctions in this region.