Hyperglycemia is the main feature of metabolic disturbances in patients diagnosed with diabetes mellitus (DM) and this is mainly due to pancreatic cell loss [1]. Meanwhile, thyroid function disturbances are considered the second most frequent endocrinal disorder [2]. There are numerous interactions between the two circumstances. Hyperthyroidism is thought to be caused by insulin metabolism abnormalities such as insulin hypercatabolism, glucagon hypersecretion, increased hepatic glucose output, and elevated epinephrine levels [3].

Glucose intolerance and a worsening of blood glucose levels in diabetics are both caused by increased liver glucose synthesis in addition to rapid glycogen degradation in thyrotoxicosis [4]. Reduced hepatic glucose synthesis, gluconeogenesis, and decreased glycolytic pathways are the three main metabolic effects of hypothyroidism on glucose metabolism [5].

Based on the patient’s clinical profile, it may be challenging to identify thyroid issues in diabetics because symptoms of hyperthyroidism might resemble those of hyperglycemia, such as weight loss despite increased hunger and fatigue. Similarly, because the patient could display overweight, peripheral limb swelling, pallor, and exercise intolerance, hypothyroidism may be mistaken for the beginning of diabetic nephropathy [6].

Several reports were previously conducted to assess thyroid profile abnormalities in diabetic patients with varying results. Several factors seem to affect and control the prevalence of thyroid profile abnormalities in T2DM including ethnic differences, general population factors and personal variations [7]. Therefore we conducted this study to assess thyroid disorders among T2DM patients from Iraq.

Patients

One hundred previously diagnosed diabetic patients were included in this study aged 28-79 years of both sexes. They were living in Baghdad-Iraq. The study was conducted in a cross-sectional design and done over 4 months from January 2023 to April 2023. Each patient was thoroughly described the aim of the current study, and informed consent was acquired. Confidentiality of data was maintained.

The following were included as exclusion criteria: current state of thyroid disease, surgical removal of thyroid gland either partial or total, thyroid gland irradiation, pregnant and breastfeeding females, use of thyroid-affecting drugs, coronary artery disease, kidney function abnormalities, liver function abnormalities, diagnosis with malignant tumor, or other forms of DM.

Laboratory measurements

Included patients were subjected to total history taking, anthropometric assessment (measurement of height and weight) with calculation of body mass index (BMI) then laboratory assessment of serum glucose, HbA1c and lipid profile. Venous blood samples were obtained from overnight fasting patients to measure fasting plasma sugar. Another three mL of venous blood was withdrawn for measurement of postprandial blood glucose.

Thyroid function tests were performed including thyroid-stimulating hormone (TSH), free tri-iodothyronine (FT3), free tetra-iodothyronine (FT4).

The SPSS program version 25.0 (SPSS, USA) was used to analyze all of the data gathered. Using the chi-square test, categorical data between groups were analyzed.

All p-values were considered significant for all tests when below 0.05.

All data of the enrolled patients are presented in the Tables 1 and 2 and Figure 1. The current study included 100 diabetic patients (35 males and 65 females).

In the current study, mean age of included patients was 47.5 \(\pm\) 7.1, while mean duration of diabetes was 7.8 \(\pm\) 2.3 years. Thyroid status assessment in included patients revealed that 52 female diabetic patients (80%) had normal thyroid profile, 4 patients (6.2%) had overt hypothyroidism, 5 patients (7.7%) had subclinical hypothyroidism, 1 patient (1.5%) had overt hyperthyroidism and 3 patients (4.6%) had subclinical hyperthyroidism.

Regarding male diabetic patients, 30 patients (85.7%) had normal thyroid profile, 3 patients (8.6%) had subclinical hypothyroid status, 1 patient (2.9%) had clinical hyperthyroidism and 1 patient (2.9%) had subclinical hypothyroid status.

Collected data were presented as mean values and standard deviation or number and percentage. BMI, body mass index; HbA1c, glycated hemoglobin; FT3, Free Tri-iodothyronine; FT4, Free tetra-iodothyronine; TSH, Thyroid Stimulating Hormone.

Data in Table 2 are presented as number and percentage.

Figure 1:Prevalence of Thyroid Disorders in Included Patients

In the current study, there was a higher prevalence of thyroid profile abnormalities, mainly hypothyroidism, in included diabetic patients especially female diabetics.

Diabetes lowers free T4 to free T3 conversion in different tissues and compromises the hypothalamic control of TSH release. T3 levels fall and T4 levels rise with severe hyperglycemia. Additionally, high insulin levels linked to diabetes raise FT4 levels, lower T3 levels, and increase TSH turnover by preventing the liver from converting T4 to T3 [8].

In included patients, 18% of patients with T2DM showed thyroid dysfunction. This was similar to other studies that found that diabetic patients generally had a prevalence of thyroid dysfunction of 35% [9], 31% [10], which was higher than our study, while some authors reported a lower frequency of 12.3% and 12.7% [11, 12].

In the one-hundred diabetes patients, subclinical hypothyroid status was the most prevalent type of thyroid impairment. This could be due to the fact that diabetes causes a decrease in TRH production may help to explain this. From 12.5% to 32.4% of T2DM patients exhibit hypothyroidism, according to other studies [13]. Other investigations have shown that the commonest form of thyroid dysfunction is subclinical hypothyroidism [14].

Females with T2DM are more likely to have thyroid dysfunction because estrogen hormone directly affects thyroid follicular cells and has an impact on TBG [15]. This theory was corroborated by our data, which showed that females had a greater overall prevalence of thyroid disease, specifically hypothyroid status. These results were in agreement with previous studies reporting higher prevalence of thyroid dysfunctions in females [11, 12, 16].

Based on our prior research, we recommend routine thyroid profile screening in patients with T2DM, especially in those with higher glycated hemoglobin, to help with early thyroid dysfunction detection and management, allowing for better glycemic control and reducing diabetic sequelae.

This research paper received no external funding.

The authors declare no conflicts of interest.

All authors contributed equally to this paper. They have all read and approved the final version.

Informed consent was obtained from all participates in the study as needed.

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