Evaluation Of Thyroid Dysfunction In Type 2 Diabetic Patients

Introduction

1.1 Background of the study

Diabetis mellitus (DM) and thyroid dysfunction (TD) are the two most common endocrine disorders seen in adult population (Diez et al., 2011). The association between diabetes and thyroid disorders was first described in 1979 and a number of studies had estimated the prevalence of thyroid dysfunction among type 2 diabetic patients to the range between 2.2-17% [2,3]. Higher levels of HbA1c (A1c) are found in type 2 diabetic patients with thyroid dysfunction, and diabetes seems to influence thyroid function at two sites: first at the hypothalamic control of TSH by TRH, and second, at the peripheral tissues by converting T4 to T3.

Hyperglycemia leads to a reduction in concentrations of T4, 5-deiodinase, low concentrations of serum T3, raised levels of reverse T3 and low, normal or high levels of T4. Thyroid hormone regulates metabolism, while diabetes alters the metabolism of a number of materials, including glucose, fatty acids, triglycerides and lipoproteins. Thyroid hormones, also, can help in the regulation of carbohydrate metabolism and pancreatic metabolism, whereas diabetes also affects thyroid function tests to a variable extent. It is also worthy to mention that the underlying thyroid problem may go undiagnosed because of the similarities between signs and symptoms of thyroid disorders and diabetes (Philemon, 2014).

Hyperthyroidism refers to a hypermetabolic state characterized by excessively released energy at rest, weight loss, reduced cholesterol levels and increased lipolysis and gluconeogenesis, while hypothyroidism leads to reduced energy release, weight gain, increased cholesterol levels, and reduced lipolysis and gluconeogenesis. It is also mentioned that euthyroid individuals may have fluctuations in the concentrations of thyroid hormone in the plasma, correlating to changes in the secretion and sensibility of insulin (Ravishanka et al., 2013). It had been noticed that hyperthyroidism may worsen glycemic control and make insulin requirement more than expected. It seems important to check thyroid function in type 2 diabetic patients, although this is not recommended in the guidelines. Thyroid dysfunction in diabetics seems to be more prevalent in elderly people when compared to those below sixty.

The prevalence of thyroid dysfunction in type 2 diabetics in both sexes varies between males and females and it is not clear whether there is male or female preponderance, although in a study in Saudi Arabia it was found that there is male predominance of primary hypothyroidism, but this depends on patient number and selection, as it is well-known that females outnumber males in non-diabetic population, and it is well-known, also that this depends on a number of factors including ethnicity, geographic and environmental factors including iodine intake status and probably other undiscovered factors (Ahmed et al., 2019).

Hypothyroidism is the most prevalent problem encountered in type 2 diabetic patients, compared to hyperthyroidism. Insulin and thyroid hormones are intimately involved in cellular metabolism, thus an excess or deficit of either one of these hormones leads to a functional derangement of the others. Metformin is the most commonly used anti-glycemic drug in type 2 diabetics and it was found that diabetic patients treated with metformin had smaller thyroid volume and a lower risk of nodule formation compared to control. It was also found that metformin has an isolated effect on reducing TSH levels in hypothyroid patients without changes in T3 and T4 levels. Metformin lower gluconeogenesis, reduces insulin resistance which was found to be more prevalent in hypothyroid patients, it is also thought that this drug changes the affinity and/or quantity of thyroid hormone receptors and increases the central dopaminergic tone or leads to activation of TSH receptors and by this way it enhances the effects of thyroid hormone in the pituitary (Bharat et al., 2013).

1.2 Statement of the problem

Diabetes mellitus is a common endocrine disorder rising in India and has reached approximately 20% in urban populations and approximately 10% in rural Population. On long term it is associated with vascular complications these are responsible for increased morbidity and mortality among diabetic subjects. New addition to these complications is the thyroid dysfunction which is indicated by the recent studies. The first report showing the association between diabetes and thyroid dysfunction was published in 1979. Since then a number of studies have estimated the prevalence of thyroid dysfunction among diabetes patients to be varying from 2.2 to 17%, the most common disorder being subclinical hypothyroidism. However, few studies also estimated much higher prevalence of thyroid dysfunction in diabetes i.e., 31% and 46.5% respectively also not showed any significant correlation between FPG and thyroid profile parameters. Thyroid hormones directly control insulin secretion.

In hypothyroidism, there is a reduction in glucose-induced insulin secretion by beta cells, and the response of beta cells to glucose orcatecholamine is increased in hyperthyroidism due to increased beta cell mass. Moreover, insulin clearance is increased in thyrotoxicosis. Diabetes may affect the thyroid function to variable extent. Diabetes mellitus appears to influence thyroid function in two sites; first at the level of hypothalamic control of TSH release and second at peripheral tissue by converting T4 to T3.

Unrecognized thyroid dysfunction not only worsens the metabolic control but also impede the management of diabetes. Studies also have suggested that type 2 diabetes mellitus patients with subclinical hypothyroidism are at risk of complications like nephropathy and cardiovascular events(Meng et al., 2017; Sarode et al., 2017). The ability to diagnose and treat subclinical hypothyroidism in these patients may greatly enhance the quality of life. Hence there is need to detect such cases where hypothyroidism contributes to morbidity and where it is the cause for poor control of the associated conditions. The treatment of hypothyroidism helps in better control of other associated co-morbidities. So, patients with diabetes need to be screened for thyroid dysfunction. Therefore, in present study association between thyroid dysfunction and Diabetes was assessed by correlating FPG and Thyroid profile.

1.3 Aims and objectives of the study

1. The aim of this study is to establish the relationship between the diabetes and thyroid dysfunction probably affected as a consequence to the auto immune pathology.
2. To study the thyroid functions in diabetes mellitus.
3. To know the spectrum of thyroid dysfunction in diabetes mellitus.

1.4 Significance of the study

A study of this nature has relevance that cannot be over-emphasized. Findings from this study will show areas of gaps in knowledge, attitude and practice of patient education and teaching among aged people, especially in the perspective of disease management among patients, and this will help nursing educators emphasize on deficit areas nurses training. Sufficient knowledge about patient education would enable nurses teach patients key things, if not everything, the patients should know about the disease conditions, treatment, management and control. Health Authorities and stakeholders such as Nursing and midwifery council of Nigeria would find these results useful for policy review and implementation. Also, this study will contribute to the existing body of literature and serve as a reference for future research in related fields.

1.6 Scope of study

This study is delimited to evaluation of thyroid dysfunction in type 2 diabetic patients. The study is carried out in Usman Danfodio University Teaching Hospital, Sokoto (UDUTH). The choice of Usman Danfodio University Teaching Hospital, Sokoto, was guided by the fact that it serves as a central meeting point for the health care workers and the patients, and because it would be impossible to cover the entire population of the study.