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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 16  |  Issue : 1  |  Page : 3-5

Thyroid dysfunction in patients with Type-2 diabetes mellitus in Kerala: A case–control study


1 Family Physician, VPS Lakeshore Hospital, Palakkad, Kerala, India
2 Family Physician, PHC Perumatty, Palakkad, Kerala, India
3 Physician, Valluvanad Hospital, Ottapalam, Kerala, India

Date of Web Publication1-Apr-2019

Correspondence Address:
Dr. Muhammed Jasim Abdul Jalal
Department of Family Medicine, VPS Lakeshore Hospital, NH 47 Bypass, Nettoor P.O., Maradu, Kochi - 682 040, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/trp.trp_47_18

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  Abstract 


Aim: The aim of this study is to establish the relationship between type 2 diabetes mellitus (Type 2 DM) and thyroid dysfunction.
Objective: The objective of this study is to study: (1) The prevalence of thyroid dysfunction in Type-2 DM. (2) The spectrum of thyroid dysfunction.
Study Design: This was a case-control study.
Study Setting: This study was conducted in Family Medicine outpatient clinics in Thrissur, Kerala.
Subjects and Methods: A total of 50 cases (diagnosed case of Type 2 DM) and 50 healthy controls were taken into consideration randomly. Thyroid function tests were conducted using the chemiluminescence assay. Then, it was analyzed statistically after tabulation.
Statistical Analysis: Statistical analysis was performed using the Chi-square test for categorical variables. Student's t-test was used for finding significance between the means. A “P < 0.05” was considered statistically significant.
Results: Thyroid dysfunction was found to be more in type 2 DM (16%) than in healthy controls (4%) which were significant. Among those diabetic patients with thyroid dysfunction, 6 (75%) out of 8 were females. The mean body mass index was high in diabetic patients with thyroid dysfunction. The hemoglobin A1c levels in patients who had thyroid dysfunction were high. Those with thyroid dysfunction had a mean total cholesterol level higher than euthyroid diabetics and controls. Goiter was found to be present in 4% of cases of Type 2 DM.
Conclusion: Type 2 DM and thyroid diseases have a significant association. Subclinical hypothyroidism and overt hypothyroidism were the most common thyroid abnormality in Type 2 DM. Thyroid dysfunction was associated with worsening dyslipidemia in Type 2 DM.

Keywords: Dyslipidemia, subclinical hypothyroidism, thyroid dysfunction, Type 2 diabetes mellitus


How to cite this article:
Jalal MJ, Riyas B, Kumar A P. Thyroid dysfunction in patients with Type-2 diabetes mellitus in Kerala: A case–control study. Thyroid Res Pract 2019;16:3-5

How to cite this URL:
Jalal MJ, Riyas B, Kumar A P. Thyroid dysfunction in patients with Type-2 diabetes mellitus in Kerala: A case–control study. Thyroid Res Pract [serial online] 2019 [cited 2019 Apr 26];16:3-5. Available from: http://www.thetrp.net/text.asp?2019/16/1/3/255301




  Introduction Top


Diabetes is the most common endocrine metabolic disorder, we were curious to understand and learn the association of this with another common endocrine gland function, i.e., the thyroid gland. The presence of insulitis, presence of antibodies and auto-reactive T-cell's against islet antigens and an association with some other known organ-specific autoimmune diseases (thyroid disorders and pernicious anemia) suggest that Type 1 DM is an autoimmune disorder.[1],[2]


  Subjects and Methods Top


This was a case-control study undertaken in various Family Medicine Clinics in the Thrissur district of Kerala, during the period from June 2017 to June 2018. This study included 50 diagnosed cases of Type-2 DM and 50 age- and sex-matched healthy controls. Type 2 diabetes mellitus (Type 2 DM) cases with age >35 years, who were on oral hypoglycemic agents for at least 6 months, were included in the study. The diagnosis of type 2 DM was based on the American Diabetes Association criteria. The known patients with thyroid disease and patients having coexistent conditions that can influence the thyroid hormone levels history of neck irradiation, pregnancy, fever, burns, trauma, liver cirrhosis, renal failure, malignancies, myocardial infarction and drugs such as oral contraceptive pills (OCP), salicylates, phenytoin, amiodarone, and beta blockers were excluded.

Patients were diagnosed to have:

  1. Overt hypothyroidism: When TSH >5.5 μl U/ml, free T4 <0.8 ng/dl and/or free T3 <1.4 pg/ml
  2. Overt hyperthyroidism: When TSH <0.5 μl U/ml, free T4 >1.5 ng/dl and/or free T3 >4.2 pg/ml
  3. Subclinical hypothyroidism: When TSH >5.5 μl U/ml with normal free T3 and free T4
  4. Subclinical hyperthyroidism, when TSH <0.5 μl U/ml with normal free T3 and free T4.



  Results Top


A total of 50 cases of Type-2 DM aged >35 years who presented to the clinics were included in the study and controls were taken with the same age and sex. The mean age of the diabetic group was 51.38 ± 7.42 years, and that of the control group was 50 ± 7.55 years. The mean duration of diabetes was 6.06 ± 3.25 years. After the clinical and laboratory assessment, the results were analyzed. Subclinical hypothyroidism and hypothyroidism were the most common thyroid dysfunction in both cases and controls [Table 1]. Thyroid dysfunction was found to be more in Type-2 DM (16%) than in healthy controls (4%), which was statistically significant.
Table 1: Thyroid dysfunction in type 2 diabetes mellitus and controls

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As shown in [Table 2], hypothyroidism and subclinical hypothyroidism is more evident in the elderly age groups (55–65 years). Two-third (75%) among those diabetic patients with thyroid dysfunction (subclinical hypothyroidism and hypothyroidism) were female (6 out of 8).
Table 2: Age distribution of thyroid dysfunction in diabetics

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Comparison of body mass index between cases and controls

The mean body mass index of diabetic patients with thyroid dysfunction (subclinical and overt hypothyroidism) was 29.03 ± 1.54 kg/m2 while that of euthyroid diabetics was 26.04 ± 2.38 kg/m2 and that in healthy controls was 21.32 ± 2.76 kg/m2.

Comparison of thyroid-stimulating hormone levels between cases and controls

The mean thyroid-stimulating hormone (TSH) levels in people with diabetes with thyroid dysfunction was 11.88 ± 5.62 while that in euthyroid diabetics was 2.66 ± 1.04 and in controls was 2.56 ± 2.12.

Mean hemoglobin A1c levels in cases

The hemoglobin A1c levels which reflect the glycemic control in patients who had thyroid dysfunction were found to be 10.33 ± 2.37 while that of euthyroid diabetics was 7.16 ± 1.04 and that of control population is in the range of 4%–6%.

Lipid profile variations in diabetics and controls total cholesterol level distribution

Patients with thyroid dysfunction had a mean total cholesterol level of 257.87 mg/dl with a standard deviation of 28.68 while that of the euthyroid diabetics found to be 204.11 ± 11.35 mg/dl and controls was 180 ± 15.96 mg/dl.

Triglyceride level distribution

A total of 7 out of 50 diabetic patients had a mean triglyceride level of 196.62 ± 19.63 mg/dl and that of euthyroid diabetics was 162.26 ± 20.49 mg/dl; the mean level in the controls was 140.18 ± 17.12 mg/dl.

Low-density lipoprotein cholesterol distribution

The diabetic patients with thyroid dysfunction had a mean low density lipoprotein cholesterol level of 159.37 ± 16.18 mg/dl and that of euthyroid diabetics was 105.83 ± 12.96 mg/dl while that of controls was 92.18 ± 18.23 mg/dl.

Prevalence of thyroid swelling among cases and controls

Goiter was found to be present in 4% of cases of Type-2 DM patients with patients having thyroid dysfunction predominating (12.5%). Goiter was detected in 4% of controls and 50% of them were hypothyroid.


  Discussion Top


In this study, 16% of patients were found to have thyroid dysfunction (8 out of 50 cases). Among the 8 cases, 5 had subclinical hypothyroidism and 3 had overt hypothyroidism. In the control population, 2 (4%) were found to have thyroid dysfunction of which one with subclinical hypothyroidism and other with overt hypothyroidism. The association of Type-2 DM and thyroid disease was significant. This result goes in hand with the study of Akbar et al. In 2005, Akbar et al. reported an overall prevalence of 16% cases of thyroid dysfunction and 42% in cases of latent autoimmune diabetes in adults (LADA).[3] The most common thyroid abnormality detected was subclinical hypothyroidism (5 out of 8 cases) followed by overt hypothyroidism (3 out of 8 cases). In 2002, Nobre et al. reported 298 cases of Type-2 DM with an overall prevalence of thyroid dysfunction in 12.7%.[4] Of these, subclinical hypothyroidism was found in 68%. About 2% of the cases of hyperthyroidism were also detected. However, we could not find any cases of hyperthyroidism, subclinical or overt, detected in the present sample of the diabetic population studied. This could be related mainly to the smaller sample size taken and partly to the old age group of the sample studied, as there is an increased prevalence of thyroid hypofunction than hyperfunction as age advances. Recently, there has been an increase in reports which confirm a higher incidence of autoimmune thyroid diseases even in Type-2 DM (Krejci and Perusicova).[5]

Furthermore, the percentage of thyroid profile abnormality detected in the general population was 4% which is lower with the data of Whickham survey by Tunbridge et al.,[6] which found it to be 6.6%. The variation can be due to many factors such as the smaller sample size, difference in the sensitivity of estimation method, and variability in the prevalence of autoimmune factors in different populations. The study by Smithson[7] in a larger population of 206 cases of Type-2 DM also showed a higher female ratio with the prevalence in female diabetics as 10.9% and males as 6.9%, whereas, in this study, that was 12% and 4%, respectively. A possible confounding factor could be an increase in female (27/50) samples, but not amounting to this high a difference which definitely shows a higher prevalence in thyroid disease in females.

The mean body mass index in diabetic patients was 29.03 ± 1.54 kg/m2, which was higher than that amongst controls (21.32 ± 2.76 kg/m2) and euthyroid diabetics (26.04 ± 2.38 kg/m2). This observation attained significance like the study by Kenigsberg.[8] who reports a large number of obese patients in diabetes, possibly due to obesity-associated insulin resistance.

The mean HbAlc level in people with diabetes with thyroid dysfunction was (10.33 ± 2.37) higher than those of euthyroid ones (7.16 ± 1.04). The study by Schlienger et al.[9] shows a poor glycemic control inducing a “low T3 state” in patients with both Type-1 and Type-2 DM. However, it should be emphasized that a low T3 syndrome may occur diseases characterized by increased catabolism. The lipid level variations in our study are in accordance with the Fremantle diabetic study by Davis et al.[10]


  Conclusion Top


  • Type-2 DM and thyroid diseases have a significant association (P = 0.045)
  • Subclinical hypothyroidism and hypothyroidism (overt) were the most common thyroid abnormality in Type-2 DM
  • Thyroid dysfunction was more prevalent in female diabetic patients than in males
  • Thyroid dysfunction was associated with worsening dyslipidemia in Type-2 DM
  • Increased thyroid dysfunction in LADA warrants islet cell antibody screening in Type-2 DM to exclude autoimmune thyroid disorders.


Limitations

  1. Sample size is too small to draw conclusions
  2. Randomization bias.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Wu P. Thyroid diseases and diabetes. Clin Diabetes 2000;18:38.  Back to cited text no. 1
    
2.
Mohan V, Tripathy BB. RSSDI introduction. In: RSSDI Text Book of Diabetes Mellitus. 2nd ed. Jaypee. hyderabad 2008. p. 1-3.  Back to cited text no. 2
    
3.
Akbar DH, Ahmed MM, Al-Mughales J. Thyroid dysfunction and thyroid autoimmunity in Saudi type 2 diabetics. Acta Diabetol 2006;43:14-8.  Back to cited text no. 3
    
4.
Nobre EL, Jorge Z, Prates S, Silva C, Castro JJ. Profile of thyroid function in a population with type-2 diabetes mellitus. Br Endocr Soc Abstract 2000;3:298.  Back to cited text no. 4
    
5.
Krejci H, Perusicova J. Autoimmune thyropathies in patients with diabetes mellitus type 1 and 2. DMEV 2004;7:164.  Back to cited text no. 5
    
6.
Tunbridge WM, Evered DC, Hall R, Appleton D, Brewis M, Clark F, et al. The spectrum of thyroid disease in a community: The Whickham Survey. Clin Endocrinol (Oxf) 1977;7:481-93.  Back to cited text no. 6
    
7.
Smithson MJ. Screening for thyroid dysfunction in a community population of diabetic patients. Diabet Med 1998;15:148-50.  Back to cited text no. 7
    
8.
Kenigsberg S. Pharmalogical approaches to treating obese patient. Clin Endocrinol Metab 1976;5:455-79.  Back to cited text no. 8
    
9.
Schlienger JL, Anceau A, Chabrier G, North ML, Stephan F. Effect of diabetic control on the level of circulating thyroid hormones. Diabetologia 1982;22:486-8.  Back to cited text no. 9
    
10.
Davis TM, Bruce DG, Davis WA. Predictors of first stroke in type 1 diabetes: The Fremantle diabetes study. Diabet Med 2005;22:551-3.  Back to cited text no. 10
    



 
 
    Tables

  [Table 1], [Table 2]



 

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