European Journal of Cardiovascular Medicine

Diabetes mellitus (DM) and thyroid abnormalities are the predominant endocrine illnesses encountered in clinical practice. Thyroid abnormalities in persons with diabetes negatively impact clinical outcomes, and associations between the two illnesses have been documented for an extended period [1,2].

The prevalence of hypothyroidism is 4-5% in Western countries, however in India it is approximately one in ten persons.[3,4] Research indicates a greater incidence of thyroid abnormalities in patients with type 2 diabetes mellitus (12% to 23%) [5], and poorly regulated blood glucose levels influence plasma triiodothyronine (T3) and thyroxine (T4) [6]. Thyroid hormones play a role in regulating glucose metabolism, and diabetes mellitus impacts thyroid hormone functioning [7]. The objective of the study was to illustrate the frequency of thyroid diseases in patients with diabetes mellitus in a rural South Indian population.

Study Design and Setting: This hospital-based, cross-sectional study was conducted in the Department of General Medicine, Jhalawar Medical College, Jhalawar (Raj.), from September 2023 to August 2024 to assess the prevalence of hypothyroidism among patients with diabetes mellitus.

Study Population: A total of 200 diabetic patients were included in the study. Patients were selected from those attending the outpatient and inpatient departments of General Medicine.

Inclusion Criteria

• Patients aged 18 years and above diagnosed with Type 2 Diabetes Mellitus.
• Patients willing to participate and provide informed consent.

Exclusion Criteria

• Patients with a known history of thyroid disorders before the diagnosis of diabetes.
• Patients on medications affecting thyroid function (e.g., amiodarone, lithium).
• Pregnant women and patients with chronic kidney disease or malignancy.

Data Collection

• A detailed history was taken, including demographic details, duration of diabetes, comorbidities, and medication history.
• A clinical examination was performed to assess signs of hypothyroidism.
• Laboratory investigations included:
  • Fasting Blood Sugar (FBS) and Postprandial Blood Sugar (PPBS) – measured using a glucose oxidase-peroxidase method.
  • HbA1c – assessed to determine long-term glycemic control.
  • Thyroid Function Tests (TFTs) – including TSH, Free T3, and Free T4, measured using chemiluminescence immunoassay (CLIA).
  • Serum Lipid Profile – assessed in all patients.

Diagnostic Criteria

• Hypothyroidism was defined as TSH >4.5 µIU/mL with or without reduced Free T4 levels.
• Subclinical Hypothyroidism was defined as TSH >4.5 µIU/mL with normal Free T4 levels.
• Overt Hypothyroidism was defined as TSH >4.5 µIU/mL with low Free T4 levels.

Statistical Analysis

• Data were entered into Microsoft Excel and analyzed using SPSS (version 25.0).
• Continuous variables were expressed as mean ± standard deviation (SD), while categorical variables were presented as percentages.
• The Chi-square test was used to assess associations between categorical variables.
• A p-value <0.05 was considered statistically significant.

Ethical Considerations

• Ethical approval was obtained from the Institutional Ethics Committee before the study commenced.
• Written informed consent was taken from all participants.
• Patient confidentiality was strictly maintained.

Table- 1 Clinical Profile of Study Participants

In this study, among 200 diabetic patients, 48 (32%) were found to have thyroid disorders. Of these, 16 patients (10.67%) had hypothyroidism, 24 (16.00%) had subclinical hypothyroidism, 3 (2.00%) had hyperthyroidism, and 5 (3.33%) had subclinical hyperthyroidism. The prevalence of thyroid dysfunction was higher in females (44%) compared to males (20%), with hypothyroidism being more prevalent among females (13.33%) than males (8%). Additionally, hypothyroidism and subclinical hypothyroidism were more common in elderly females, with a prevalence of 15.63% and 28.13%, respectively. The prevalence of hypothyroidism in the elderly was 15.52%, higher than in the adult/middle-aged group (7.61%). The mean age of hypothyroid patients was significantly higher (64.75 years, SD ± 14.98) compared to euthyroid patients (56.20 years, SD ± 11.96), with a p-value of 0.0116, indicating a statistically significant difference.

Table 2. Sex distribution of Thyroid Dysfunction among Diabetic Patients

Table 1 presents the sex distribution of thyroid dysfunction among 200 diabetic patients, comprising 100 males and 100 females. Among males, 8 were diagnosed with hypothyroidism, 9 with sub-clinical hypothyroidism, 2 with hyperthyroidism, 2 with sub-clinical hyperthyroidism, and 79 exhibited normal thyroid function. In females, 12 had hypothyroidism, 25 had sub-clinical hypothyroidism, 3 had hyperthyroidism, 6 had sub-clinical hyperthyroidism, and 54 were classified as having normal thyroid function. The P-value for the distribution was 0.0027, indicating a statistically significant difference in the prevalence of thyroid dysfunction between male and female diabetic patients.

Table 3. Distribution according to Thyroid Function Test with Thyroid Disorders and without Thyroid Disorders among Diabetics

Table 2 compares thyroid function test parameters between diabetic patients with and without thyroid dysfunction among a total of 200 participants. For patients without thyroid dysfunction (120 patients), the mean T3, T4, and TSH levels were 86.72 ± 23.53 ng/dL, 7.88 ± 1.46 µg/dL, and 1.87 ± 0.96 µIU/mL, respectively. In contrast, patients with thyroid dysfunction (80 patients) had mean T3, T4, and TSH levels of 83.18 ± 30.22 ng/dL, 7.20 ± 3.23 µg/dL, and 8.93 ± 8.06 µIU/mL, respectively. The P-values for T3 and T4 were 0.4351 and 0.0733, indicating no significant difference, while the TSH level difference was highly significant with a P-value of <0.0001.

Table 4. Distribution according to Duration of DM among Patients with Thyroid Dysfunction and without Thyroid Dysfunction

Table 3 presents the distribution of diabetic patients with and without thyroid dysfunction based on the duration of diabetes mellitus (DM) among 200 participants. For patients with a DM duration of 0–5 years (80 patients), 66 had no thyroid dysfunction, while 14 (17.50%) had thyroid dysfunction. Among those with a DM duration of 6–10 years (90 patients), 54 had no thyroid dysfunction, and 36 (40.00%) had thyroid dysfunction. For patients with a DM duration of more than 10 years (30 patients), 18 had no thyroid dysfunction, and 12 (40.00%) had thyroid dysfunction. The P-value for the distribution was 0.0055, indicating a statistically significant association between the duration of DM and the prevalence of thyroid dysfunction.

Table 5. Comparison of Various Parameters between Hypothyroid DM Patients and Euthyroid DM Patients

Table 4 compares various parameters between hypothyroid diabetic patients (32 patients) and euthyroid diabetic patients (168 patients). The mean age of hypothyroid patients was 64.75 ± 14.98 years, significantly higher than 56.20 ± 11.96 years in euthyroid patients (P = 0.0116). The fasting blood sugar (FBS) and postprandial blood sugar (PPBS) levels were not significantly different between the groups (P = 0.6722 and P = 0.4342, respectively). The mean HbA1c was slightly lower in hypothyroid patients (7.92 ± 1.70%) compared to euthyroid patients (8.62 ± 1.87%), but the difference was not significant (P = 0.1618). The mean duration of diabetes was significantly longer in hypothyroid patients (8.37 ± 3.38 years) compared to euthyroid patients (5.77 ± 3.25 years, P = 0.0037). Hypothyroid patients also had significantly higher serum total cholesterol (217.18 ± 37.52 mg/dL, P = 0.0122), triglycerides (208.06 ± 59.65 mg/dL, P = 0.0401), LDL (117.79 ± 16.94 mg/dL, P = 0.0064), and non-HDL cholesterol (179.28 ± 37.60 mg/dL, P = 0.0017), while HDL levels were significantly lower (37.90 ± 5.31 mg/dL vs. 46.05 ± 7.29 mg/dL, P = 0.0001). The BMI was significantly higher in hypothyroid patients (26.78 ± 3.22) compared to euthyroid patients (24.17 ± 2.27, P = 0.0001). Waist-hip ratios were also significantly higher in both male (1.22 ± 0.10 vs. 1.10 ± 0.09, P = 0.0030) and female (1.08 ± 0.14 vs. 0.95 ± 0.08, P = 0.0003) hypothyroid patients compared to their euthyroid counterparts.

Table- 1 Clinical Profile of Study Participants

In this study, among 200 diabetic patients, 48 (32%) were found to have thyroid disorders. Of these, 16 patients (10.67%) had hypothyroidism, 24 (16.00%) had subclinical hypothyroidism, 3 (2.00%) had hyperthyroidism, and 5 (3.33%) had subclinical hyperthyroidism. The prevalence of thyroid dysfunction was higher in females (44%) compared to males (20%), with hypothyroidism being more prevalent among females (13.33%) than males (8%). Additionally, hypothyroidism and subclinical hypothyroidism were more common in elderly females, with a prevalence of 15.63% and 28.13%, respectively. The prevalence of hypothyroidism in the elderly was 15.52%, higher than in the adult/middle-aged group (7.61%). The mean age of hypothyroid patients was significantly higher (64.75 years, SD ± 14.98) compared to euthyroid patients (56.20 years, SD ± 11.96), with a p-value of 0.0116, indicating a statistically significant difference.

Table 2. Sex distribution of Thyroid Dysfunction among Diabetic Patients

Table 1 presents the sex distribution of thyroid dysfunction among 200 diabetic patients, comprising 100 males and 100 females. Among males, 8 were diagnosed with hypothyroidism, 9 with sub-clinical hypothyroidism, 2 with hyperthyroidism, 2 with sub-clinical hyperthyroidism, and 79 exhibited normal thyroid function. In females, 12 had hypothyroidism, 25 had sub-clinical hypothyroidism, 3 had hyperthyroidism, 6 had sub-clinical hyperthyroidism, and 54 were classified as having normal thyroid function. The P-value for the distribution was 0.0027, indicating a statistically significant difference in the prevalence of thyroid dysfunction between male and female diabetic patients.

Table 3. Distribution according to Thyroid Function Test with Thyroid Disorders and without Thyroid Disorders among Diabetics

Table 2 compares thyroid function test parameters between diabetic patients with and without thyroid dysfunction among a total of 200 participants. For patients without thyroid dysfunction (120 patients), the mean T3, T4, and TSH levels were 86.72 ± 23.53 ng/dL, 7.88 ± 1.46 µg/dL, and 1.87 ± 0.96 µIU/mL, respectively. In contrast, patients with thyroid dysfunction (80 patients) had mean T3, T4, and TSH levels of 83.18 ± 30.22 ng/dL, 7.20 ± 3.23 µg/dL, and 8.93 ± 8.06 µIU/mL, respectively. The P-values for T3 and T4 were 0.4351 and 0.0733, indicating no significant difference, while the TSH level difference was highly significant with a P-value of <0.0001.

Table 4. Distribution according to Duration of DM among Patients with Thyroid Dysfunction and without Thyroid Dysfunction

Table 3 presents the distribution of diabetic patients with and without thyroid dysfunction based on the duration of diabetes mellitus (DM) among 200 participants. For patients with a DM duration of 0–5 years (80 patients), 66 had no thyroid dysfunction, while 14 (17.50%) had thyroid dysfunction. Among those with a DM duration of 6–10 years (90 patients), 54 had no thyroid dysfunction, and 36 (40.00%) had thyroid dysfunction. For patients with a DM duration of more than 10 years (30 patients), 18 had no thyroid dysfunction, and 12 (40.00%) had thyroid dysfunction. The P-value for the distribution was 0.0055, indicating a statistically significant association between the duration of DM and the prevalence of thyroid dysfunction.

Table 5. Comparison of Various Parameters between Hypothyroid DM Patients and Euthyroid DM Patients

Table 4 compares various parameters between hypothyroid diabetic patients (32 patients) and euthyroid diabetic patients (168 patients). The mean age of hypothyroid patients was 64.75 ± 14.98 years, significantly higher than 56.20 ± 11.96 years in euthyroid patients (P = 0.0116). The fasting blood sugar (FBS) and postprandial blood sugar (PPBS) levels were not significantly different between the groups (P = 0.6722 and P = 0.4342, respectively). The mean HbA1c was slightly lower in hypothyroid patients (7.92 ± 1.70%) compared to euthyroid patients (8.62 ± 1.87%), but the difference was not significant (P = 0.1618). The mean duration of diabetes was significantly longer in hypothyroid patients (8.37 ± 3.38 years) compared to euthyroid patients (5.77 ± 3.25 years, P = 0.0037). Hypothyroid patients also had significantly higher serum total cholesterol (217.18 ± 37.52 mg/dL, P = 0.0122), triglycerides (208.06 ± 59.65 mg/dL, P = 0.0401), LDL (117.79 ± 16.94 mg/dL, P = 0.0064), and non-HDL cholesterol (179.28 ± 37.60 mg/dL, P = 0.0017), while HDL levels were significantly lower (37.90 ± 5.31 mg/dL vs. 46.05 ± 7.29 mg/dL, P = 0.0001). The BMI was significantly higher in hypothyroid patients (26.78 ± 3.22) compared to euthyroid patients (24.17 ± 2.27, P = 0.0001). Waist-hip ratios were also significantly higher in both male (1.22 ± 0.10 vs. 1.10 ± 0.09, P = 0.0030) and female (1.08 ± 0.14 vs. 0.95 ± 0.08, P = 0.0003) hypothyroid patients compared to their euthyroid counterparts.

In this study, a total of 48 out of 200 diabetic patients (32%) were found to have thyroid disorders. Of these, 16 patients (10.67%) had hypothyroidism, with an equal distribution between males (8%) and females (13.33%).This study resembled the research conducted by Diez J J et al (2011) [8]among type 2 diabetes mellitus patients in Spain, which reported a prevalence of thyroid dysfunction at 32.40%. Additionally, a retrospective study by Demitrost et al (2012)[9] indicated a prevalence of thyroid disorders at 32%, with subclinical hypothyroidism and hypothyroidism cases at 16.00% versus 16.3% and 10.67% versus 11.4%, respectively. The prevalence of hypothyroidism in the elderly was 15.52%, higher than in the adult/middle-aged group (7.61%). The mean age of hypothyroid patients was significantly higher (64.75 years, SD ± 14.98) compared to euthyroid patients (56.20 years, SD ± 11.96), with a p-value of 0.0116, indicating a statistically significant difference. These findings are analogous to the study conducted by Kim et al. (2011).[10] The average age of euthyroid patients with type 2 diabetes mellitus was 57.8 years (SD ±11.8), while the average age of type 2 diabetics with subclinical hypothyroidism was 61.7 years (SD ±9.8), with a p-value of 0.014, suggesting a correlation between subclinical hypothyroidism and advancing age in type 2 diabetes mellitus. In the research conducted by Unnikrishnan AG et al. (2013),[11] The frequency of hypothyroidism was greatest in the 46 to 54 age group (13.11%) and least in the 18 to 35 age group (7.53%).

The prevalence of thyroid diseases was greater in females (44%) compared to males (20%), and the incidence of hypothyroidism was higher in females (13.33%) than in boys (8%). Hypothyroidism and subclinical hypothyroidism were more prevalent among older females, at 15.63% and 28.13%, respectively. This study parallels the findings of Ambika Gopalakrishnan et al. (2013), [12]which indicates a greater prevalence of hypothyroidism among females compared to males (15.86% vs. 5.02%; p < 0.0001). Patients with thyroid abnormalities exhibited elevated TSH levels relative to those without thyroid diseases, a finding that was statistically significant (p < 0.0001). No statistically significant change was observed in T4 and T3 levels. The results of our study align with those of Pasupathi et al. (2008)[13] and Shalini Gupta et al. (2011).[14]In our study, prolonged diabetes duration shown a strong correlation with hypothyroidism (p= 0.0037). These findings align with the research conducted by R. Anil Kumar et al. (2013),[15] which indicated a significant association between subclinical and overt hypothyroidism and the duration of diabetes, recorded as 11.48 ± 7.96 years and 8.76 ± 7.23 years, respectively, compared to 7.91 ± 7.07 years in euthyroid diabetic patients (p= 0.019). Saroj Khatiwada et al. (2015)[16] observed that an age of 60 years or older and a diabetes duration of 5 years or more are associated with an increased relative risk of thyroid dysfunction. In this study, we found that out of 200 diabetic patients, symptoms of thyroid disorder were present in 32 patients. Among the 16 hypothyroid patients detected in the study, 10 (62.5%) patients had signs and symptoms suggestive of hypothyroidism. Diabetic patients commonly display the signs and symptoms of hypothyroidism and similar result reported by Udiong et al (2007).[17]Thyroid dysfunction is linked to a higher incidence of diabetic sequelae, such as retinopathy, nephropathy, and neuropathy, in comparison to euthyroid individuals, as evidenced by clinical and laboratory data (43.42% vs. 20.27%). Yang et al. (2010)[18] demonstrated that subclinical haemorrhage (SCH) was linked to sight-threatening diabetic retinopathy, in contrast to Chen et al. (2007),[19] who found an association between SCH and an elevated risk of nephropathy, but not retinopathy.All patients with hypothyroidism exhibited favourable glycaemic control (mean HbA1c 7.92, SD ±1.70) in contrast to euthyroid patients (mean HbA1c 8.62, SD ±1.87) and were at a higher risk of hypoglycemia, whereas patients with hyperthyroidism demonstrated inferior glycaemic control relative to those with hypothyroidism. Our findings align with those of the study conducted by Manjunath SC et al. (2013), [20]which reported analogous outcomes among the 13 patients with SCH. This may result from the influence of thyroid hormone on insulin.The current study of hypothyroid patients revealed that the mean serum levels of total cholesterol (TC), low-density lipoprotein (LDL), triglycerides (TG), and non-high-density lipoprotein (non-HDL) cholesterol were significantly elevated compared to those in euthyroid subjects, while the mean serum high-density lipoprotein (HDL) levels were significantly lower in hypothyroid patients than in euthyroid individuals. In a study by Chubb SAP et al. (2005),[21] patients with subclinical hypothyroidism exhibited significantly elevated serum total cholesterol compared to euthyroid subjects (mean ± SD 243.62 ± 50.27 mg% vs. 224.28 ± 46.4 mg%, p < 0.001) and significantly higher serum LDL levels than euthyroid subjects (mean ± SD 166.27 ± 50.27 mg% vs. 135.34 ± 38.67 mg%, p < 0.001). Saroj Khatiwada et al.[16] (2015) 19observed that diabetic patients with thyroid dysfunction exhibited elevated levels of total cholesterol, HDL cholesterol, and LDL cholesterol. contrast with patients devoid of thyroid problems.

Patients with hypothyroidism exhibited a higher mean BMI of 26.78 (SD ± 3.22) compared to euthyroid diabetes patients, who had a mean BMI of 24.17 (SD ± 2.27), a difference that was statistically significant (p value 0.0001). Demitrost L et al. (2012)[9] observed that patients with a BMI more than 25 were at an elevated risk of thyroid dysfunction (p < 0.016). Kumar R A et al. (2013)[15] showed a higher mean BMI of hypothyroid individuals at 27.65 ± 4.34 compared to euthyroid diabetic patients at 26.62 ± 4.16. The waist-hip ratio in hypothyroid patients was significantly higher than that in euthyroid ones.

In conclusion, this study highlights a significant prevalence of thyroid dysfunction among diabetic patients, with 32% of the participants diagnosed with thyroid disorders. The findings indicate a higher prevalence of hypothyroidism, especially among females and elderly individuals, with a notable association between the duration of diabetes and thyroid dysfunction. Hypothyroid diabetic patients exhibited higher serum cholesterol levels, triglycerides, LDL, and BMI, along with lower HDL levels compared to euthyroid diabetic patients. The study emphasizes the need for regular thyroid screening in diabetic patients, particularly those with prolonged diabetes duration and older age, to manage associated metabolic risks effectively.

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