Relative Risk for Goiter in Euthyroid Patients With T2DM
Relative Risk for Goiter in Euthyroid Patients With T2DM
We designed a cross-sectional study including all euthyroid patients found in a screening programme for thyroid dysfunction performed during 2004–2010 in our diabetic clinic. All patients were ambulatory and in good health, and had been diagnosed with T2D according to American Diabetes Association criteria. None of them had had a recent acute illness. Patients taking drugs known to affect thyroid function were excluded. The study was performed in a noniodine-deficient area, with a median urinary iodine concentration of 110 μg/l. The study protocol was approved by the local ethical committee, and all patients gave informed consent before blood sampling.
We registered demographic and anthropometric data, duration of diabetes, hypertension, hyperlipidaemia, presence or absence of diabetic complications (diabetic retinopathy, nephropathy, ischaemic heart disease, cerebrovascular disease, peripheral artery disease), treatment for diabetes (diet, oral agents and insulin) and analytical data (glucose, cholesterol, triglyceride and haemoglobin A1c). Goitre was assessed by physical examination with the patient in the sitting position. The neck was first inspected from the front and then palpated with the examiner behind the patient. Both sides of the neck were palpated while the patient swallowed, first with the examiner's hands on the same side of the patient's neck and then by palpation of the left side of the neck with the right hand and vice versa. Goitre was considered present when visible or palpable, and absent when not palpable. Serum concentrations of TSH were measured in all patients without previous thyroid dysfunction. Thyroid autoimmune status was evaluated by means of the measurement of serum levels of thyroid peroxidase autoantibodies (TPOAb) and thyroglobulin autoantibodies (TGAb). Thyroid autoimmunity was considered negative when both autoantibodies were negative, and positive when any of them were positive.
From a total population of 1112 patients included in our screening programme, we excluded 179 patients who exhibited previously known thyroid dysfunction. In the remaining group of 933 patients, there were 828 subjects with normal serum TSH concentration and 105 with newly diagnosed thyroid dysfunction (68 of them with elevated TSH and 37 with low TSH levels). In the group of 828 patients with euthyroidism, 28 patients lacked data on goitre and were also excluded. Therefore, for the purpose of this study, we selected and retrospectively evaluated 800 patients with information on goitre and with normal serum TSH concentrations. From a group of 911 nondiabetic subjects who attended our clinic during 2004–2010 for obesity, overweight or nutritional counselling, and who do not have previous history of thyroid dysfunction, we excluded 41 subjects who were found to have elevated or reduced TSH concentrations and 199 who lacked information on neck palpation. Therefore, 671 subjects without diabetes, with normal serum TSH, and with information on the presence or absence of goitre were evaluated as control group.
Fasting samples of venous blood were obtained from an antecubital vein between 08:00 and 09:00 for the estimation of hormonal and general analytical data. Serum TSH concentrations were determined using commercially available immunochemiluminescent assay (Immulite, Diagnostic Products Corporation, Los Angeles, CA, USA). The sensitivity of the assay was 0·004 mU/l. The mean intra- and interassay coefficients of variation were less than 10%. Normal values for TSH were 0·4–5·0 mU/l. TPOAb and TGAb were measured using a chemiluminescent immunoassay system (Immulite Thyroid Autoantibody, Siemens Medical Solutions Diagnostic Ltd., Llanberis, Gwynedd, UK). Positivity for TPOAb and TGAb was considered when the titre of these autoantibodies was at least 100 U/ml, and at least 340 U/ml, respectively.
For quantitative variables, results are expressed as mean ± SD for normally distributed data, and as median (interquartile range) for nonparametric data. Categorical variables are described as percentages (%). For comparisons of means between two groups of subjects, the Student's t-test was used for normally distributed data, and the Mann–Whitney U-test was employed for nonparametric data. For ratio comparisons, the chi-squared test or Fisher's exact test was used. The relative risk for goitre in patients in comparison with control subjects was estimated by means of the odd ratios (Mantel–Haenszel test). Several models of logistic regression analysis were used to assess the presence of goitre as a function of quantitative and qualitative variables. Differences were considered significant when P < 0·05.
Patients and Methods
Study Design
We designed a cross-sectional study including all euthyroid patients found in a screening programme for thyroid dysfunction performed during 2004–2010 in our diabetic clinic. All patients were ambulatory and in good health, and had been diagnosed with T2D according to American Diabetes Association criteria. None of them had had a recent acute illness. Patients taking drugs known to affect thyroid function were excluded. The study was performed in a noniodine-deficient area, with a median urinary iodine concentration of 110 μg/l. The study protocol was approved by the local ethical committee, and all patients gave informed consent before blood sampling.
We registered demographic and anthropometric data, duration of diabetes, hypertension, hyperlipidaemia, presence or absence of diabetic complications (diabetic retinopathy, nephropathy, ischaemic heart disease, cerebrovascular disease, peripheral artery disease), treatment for diabetes (diet, oral agents and insulin) and analytical data (glucose, cholesterol, triglyceride and haemoglobin A1c). Goitre was assessed by physical examination with the patient in the sitting position. The neck was first inspected from the front and then palpated with the examiner behind the patient. Both sides of the neck were palpated while the patient swallowed, first with the examiner's hands on the same side of the patient's neck and then by palpation of the left side of the neck with the right hand and vice versa. Goitre was considered present when visible or palpable, and absent when not palpable. Serum concentrations of TSH were measured in all patients without previous thyroid dysfunction. Thyroid autoimmune status was evaluated by means of the measurement of serum levels of thyroid peroxidase autoantibodies (TPOAb) and thyroglobulin autoantibodies (TGAb). Thyroid autoimmunity was considered negative when both autoantibodies were negative, and positive when any of them were positive.
Patients
From a total population of 1112 patients included in our screening programme, we excluded 179 patients who exhibited previously known thyroid dysfunction. In the remaining group of 933 patients, there were 828 subjects with normal serum TSH concentration and 105 with newly diagnosed thyroid dysfunction (68 of them with elevated TSH and 37 with low TSH levels). In the group of 828 patients with euthyroidism, 28 patients lacked data on goitre and were also excluded. Therefore, for the purpose of this study, we selected and retrospectively evaluated 800 patients with information on goitre and with normal serum TSH concentrations. From a group of 911 nondiabetic subjects who attended our clinic during 2004–2010 for obesity, overweight or nutritional counselling, and who do not have previous history of thyroid dysfunction, we excluded 41 subjects who were found to have elevated or reduced TSH concentrations and 199 who lacked information on neck palpation. Therefore, 671 subjects without diabetes, with normal serum TSH, and with information on the presence or absence of goitre were evaluated as control group.
Hormone Assay
Fasting samples of venous blood were obtained from an antecubital vein between 08:00 and 09:00 for the estimation of hormonal and general analytical data. Serum TSH concentrations were determined using commercially available immunochemiluminescent assay (Immulite, Diagnostic Products Corporation, Los Angeles, CA, USA). The sensitivity of the assay was 0·004 mU/l. The mean intra- and interassay coefficients of variation were less than 10%. Normal values for TSH were 0·4–5·0 mU/l. TPOAb and TGAb were measured using a chemiluminescent immunoassay system (Immulite Thyroid Autoantibody, Siemens Medical Solutions Diagnostic Ltd., Llanberis, Gwynedd, UK). Positivity for TPOAb and TGAb was considered when the titre of these autoantibodies was at least 100 U/ml, and at least 340 U/ml, respectively.
Statistical Analysis
For quantitative variables, results are expressed as mean ± SD for normally distributed data, and as median (interquartile range) for nonparametric data. Categorical variables are described as percentages (%). For comparisons of means between two groups of subjects, the Student's t-test was used for normally distributed data, and the Mann–Whitney U-test was employed for nonparametric data. For ratio comparisons, the chi-squared test or Fisher's exact test was used. The relative risk for goitre in patients in comparison with control subjects was estimated by means of the odd ratios (Mantel–Haenszel test). Several models of logistic regression analysis were used to assess the presence of goitre as a function of quantitative and qualitative variables. Differences were considered significant when P < 0·05.
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