Frequency and Factors Associated with Thyroid Dysfunction: an Analytical Crosssectional Study from a Tertiary Care Center in Kabul, Afghanistan

Introduction

The thyroid secretes two most important hormones, thyroxine and triiodothyronine, usually called T4 and T3, correspondingly. These hormones greatly increase the metabolic rate of the body [1].

The thyroid stimulating hormone [TSH], secreted by the thyro-tropin cells of the anterior pituitary, plays a central role in con-trol of the thyroid axis and serves as the most useful physiologic indicator of thyroid hormone action [2].

TSH is a 31-kDa hormone having two subunits [α and β]; the α subunit is common to the other glycoprotein hormones (lutein-izing hormone, follicle stimulating hormone, human chorionic gonadotropin [hCG]), but the TSH β subunit is unique to TSH. The amount and nature of carbohydrate modification are modu¬lated by thyrotropin-releasing hormone (TRH) stimulation and affect the biologic activity of the hormone [3].

Regarding the laboratory assessment of the patient with known or suspected thyroid illness, the doctor had better seek to arrive at both functional and anatomic diagnoses. Laboratory tests will ratify if there is an excess, normal, or an inadequate supply of thyroid hormone to confirm the implications from the clinical history and physical examination. The second is to determine the existence or nonexistence of anatomic anomalies in the thyroid gland itself. Laboratory tests for thyroid assessment can be di¬vided into two main classes including tests that evaluate the state of the hypothalamic-pituitary-thyroid axis such as TSH followed by estimation of the free T4 or T3 concentrations in the serum for confirmation [4].

Hypothyroidism is not rare, affecting more than 1% of the gen-eral population and about 5% of persons over age 60 years. Thyroid hormone deficiency disturbs almost all body functions. The severity ranges from mild hypothyroid states to prominent myxedema. Other causes of hypothyroidism might be failure or resection of the thyroid gland itself or deficiency of TSH secre¬tion from pituitary gland [5].

From a clinical perspective, hyperthyroidism is a hyper metabol-ic condition resulting from excessive production of thyroid hor-mones. Furthermore, women are more susceptible to developing hyperthyroidism than men are. For laboratory investigation of primary hyperthyroidism, it is better to estimate the concentra-tion of TSH which is suppressed and the serum FT4 concentra-tion will be elevated [6].

Finding a low TSH and an elevated FT4 concentrations are usu-ally sufficient enough to establish the diagnosis of hyperthyroid-ism in the setting of well-matched clinical features. Whenever the TSH concentration is low but the FT4 concentration is within the reference range, T3 concentration should be measured. Fur-thermore, a persistently repressed concentration of serum TSH with normal concentrations of serum T3 and FT4 describe sub-clinical hyperthyroidism [7].

However, as advocated by most studies assessment of TSH is the single most suitable test of thyroid function in the vast majority of patients. In most cases the TSH will be within the reference interval, and no further testing is required [8].

Thus to summarize, hypo and hyperthyroidism are common en¬docrine disorders and TSH serves as a primary clue, especially in resource constrained set up like Afghanistan, where diagnos¬tic and health care facilities are meagre and financial constraints further impose barriers [9].

With all these obstacles and constraints in context, this is the first study aimed to describe the frequency of occurrence and factor associated with thyroid dysfunction in a native Afghan popula¬tion using serum TSH as a screening test. As thyroid dysfunc¬tions is linked with many complications and morbidities. Early screening using TSH, prompt further evaluation and treatment can prevent these complications and morbidities [10].

Methods

The study used an ‘Analytical Cross-sectional’ design to as-sess frequency and factors associated with thyroid dysfunction among individuals coming to Clinical Laboratory of French Medical Institute for Mothers and Children [FMIC], a high qual¬ity and tertiary healthcare center in Afghanistan from July to September 2018.

FMIC was established in 2005 and is the first healthcare facil¬ity in Afghanistan which achieved ISO 9001: 2008 certificate in 2009. FMIC’s Clinical laboratory is considered the best in the region for providing high quality services. A non-probability consecutive sampling was used to recruit study participants. The study was approved by the Ministry of Public Health [MoPH] Afghanistan and French Medical Institute for Mothers and Chil¬dren (ERC# 20-FMIC-ER-18). An informed consent was re¬ceived from the study participants and they were informed about study purpose in detail.

All the individuals who came to Clinical Laboratory of FMIC for serum TSH test during the study period were included. Patients who were already diagnosed having any thyroid dysfunctions, patients taking thyroxin, patients who have had thyroid surgery, patient who were taking antithyroid medicines and patients who were suffering from chronic diseases such as hypertension, di¬abetes mellitus and cardiac disorders were excluded from the study.

Data was collected by the principal investigator using a struc¬tured questionnaire via one to one interview. Questionnaire comprised of inforamtion regariding contact number, age, sex, province,medical history,history of drug use,pregnancy and smoking. The questionnaire was originally developed in En¬glish language, translated into Dari [regional language] for ap¬propriate comprehension.5 ml of blood was obtained from each participant at the time of visit, by qualified phlebotomist using standardized tubes, with standard precaution. The blood sample tube was centrifuged and serum TSH were measured by direct chemiluminescence immunoassay on automated immune an¬alyzer ADVIA Centaur (Siemens Diagnsotics USA). TSH was categorized as higher TSH level> 4.2 mIU/L, lower TSH level < 0.4 mIU/L and normal TSH level 0.4 to 4.2 mIU/L.

Descriptive and inferential statistics were used for data analysis. Statistical analysis was done using Statistical Package for the Social Science (SPSS) version 21. Proportions and frequencies were computed for categorical variables. Means and standard deviations were computed for continuous variables. Median was calculated for variable following non normal distribution.

Level of TSH was computed as variable and proportion was reported. In order to determine the relationship of independent variables with TSH level, Chi-square test of independence was run. A p-value of less than 0.05 was considered statistically sig¬nificant.

Results

Table 1: Demographic characteristics of participants (Percentages are rounded off to the nearest digit)

Describes the characteristics of the study participants. Overall 170 individuals participated during the study period (July to September 2018). Out of total, 43 of the participants, according to exclusion criteria, were excluded from the study and hence a total of 127 individuals were part of the sample for the final analysis.

Majority study participants (77%) were females. A large number of the participants (92%) did not have family history of thyroid dysfunction and majority of the female participants, (85%) were not pregnant in the last two years.

Furthermore, a 98% participants, were non-smokers. The cate¬gories were formed using the reference ranges of the adult pa¬tients as the age of participants in the study ranged from 21 years to 54 years. 74% participants in the study had normal TSH levels classified as normal thyroid function, [14%] had lower TSH lev¬els and [12%] higher TSH levels [Table 1] classified as hyper and hypothyroid respectively, depicted in Fig 1.

Figure 1: Distribution of TSH level among the study participants

Table 2 describes the association between plausible independent variables and thyroid dysfunction (levels of TSH). Factors such as age (p-value=0.02) and smoking (p-value=0.016) status were found to have statistically significant association with the thy- roid dysfunction. However, gender, family history and pregnan¬cy showed an insignificant association with thyroid dysfunction. The inferential statistics are summarized in table 2.

Table 2: Inferential statistics for the association between TSH level and other variables

                                                                     *Fisher Exact test p-value

Discussion

The current study findings revealed that a considerable per-centage of the participants had thyroid dysfunctions, [14%] had lower TSH levels which mean hyperthyroidism and [12%] had higher TSH levels which means hypothyroidism. Literature has also supported high prevalence of thyroid dysfunction among patients in developed as well as developing countries. It has been estimated that about 42 million people in India suffer from thyroid dysfunction, in addition, studies from Mumbai have sug¬gested that congenital hypothyroidism is common in India, the disease occurring in 1 out of 2640 neonates, when compared with the worldwide average value of 1 in 3800 subjects [11].

Hypothyroidism is a commonly prevailing disorder in adult Indian population as well (12). Moreover, a recent study con-ducted in Iran reported higher incidence rate of thyroid disorders than previous studies [13].

Similarly, According to a survey, which was conducted in Whickham in order to determine the prevalence of thyroid dys-function in the community it was revealed that thyroid dysfunc¬tion affects 1-2% adult population of the Great Britain [14].

Likewise, in the current study, researcher found a significant as-sociation between age and thyroid dysfunction [p-value 0.02]. Individuals with age (931-54 years) were more prone to thyroid dysfunction compare to younger individuals with age (21-30 years). Similar finding was found in another study which was conducted in Greece, in which the author found a strong associa-tion between aging and decrease TSH and T3 levels while serum FT4 levels were normal [15].

In addition, smoking was found to have a significant relation with thyroid dysfunction (p-value 0.016). None of the individ- uals with normal TSH level were smokers, 2 persons of the pa-tients with higher TSH level were smoking and 1 person of the patient with lower TSH level was smoking. Literature also sup¬ports the current findings of the study suggesting that smoking cessation is effective in primary, secondary and tertiary preven¬tion of thyroid disorders [16].

On the contrary, another study conducted by Cari M. Kitahara found that cigarette smoking is associated with reduced risks of papillary thyroid cancer and, probably, follicular thyroid cancer [17].

Furthermore, this study did not reveal any significant relation between family history and thyroid dysfunctions, which is dif¬fering from the literature that indicates strong association be¬tween family history and thyroid dysfunctions. In a multicenter cohort study which was conducted in United Kingdom about half of all the subjects reported a family history of thyroid dys¬function [18].

In addition to being the first report from Afghanistan, there were a few limitations of this study, mainly the TSH only approach which could lead to potential confounders. The data of this study is limited to those individuals who visited FMIC; thus limiting the generalizability of the results. Furthermore, the use of ques¬tions regarding family history from the subjects may have pos¬sible recall bias.

The findings recommend screening and investigation for thyroid dysfunctions in Afghan population at high risk for thyroid dis¬orders (smokers, elder people, especially pregnant women and neonates as neonatal thyroid disorders cause irreversible com¬plications).

Conclusions

The current study showed a high frequency of thyroid dysfunc-tions in individuals at a single center in a short span of time. The findings also indicated that aging and smoking are the factors associated with thyroid dysfunctions. Further studies are needed to find out the prevalence of and factors associated with thy-roid dysfunctions for appropriate and timely interventions in re¬source constrained environment of Afghanistan.

Abbreviations

TSH: Thyroid Stimulating Hormone, T3: Triiodothyronine, T4: Thyroxine, FT4: Free Thyroxine, FMIC: French Medical Institute for Mothers and Children, MoPH: Ministry of Public Health, hCG: Human Chorionic Gonadotropin, SPSS: Statistical Package for the Social Science ERC: Ethical Review Commit-tee.

Declarations

Ethics Approval and Consent Form

This study was approved by the Ethical Review Committee of FMIC (20-FMIC-ER-18) and Consent form was signed by all the study participants.

Consent for Publication

Written consent for publication was taken from all the partici-pants.

Availability of Data and Materials

All data generated or analyzed during this study are included in this published article

Competing interests: The authors declare that they have no competing interests.

Funding: No funding was received for this study.

Authors’ Contributions

MNL conceived the idea and collected the data. Data were an-alyzed by AG. SA was the major contributor to the writing of the manuscript. AMH was the major contributor for critically revising the manuscript for important intellectual content. Dr. Jamshid Jalal has given expert opinion and final approval of the version to be published.

Acknowledgements

We would like to thank for the support of Dr. Shabnam Azizi and Dr. Ahmed Nasir Hanafi previous employees of Department of Pathology and Clinical Laboratory in FMIC.

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