IMPACT OF IODINE DEFICIENCY ON THE PREVALENCE OF PREDIABETES AND TYPE 2 DIABETES MELLITUS

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 55 IMPACT OF IODINE DEFICIENCY ON THE PREVALENCE OF PREDIABETES AND TYPE 2 DIABETES MELLITUS T.T. Kamalov1, Z.A. Aynazarova2 Republican Specialized Medical Center of Endocrinology named after E. Kh. Turakulov1 Branch of the Republican Specialized Medical Center of Endocrinology in the Republic of Karakalpakstan2 https://doi.org/10.5281/zenodo.18041876 Abstract. The article presents the results of a study on the prevalence of disorders of carbohydrate metabolism (prediabetes and type 2 diabetes mellitus) in regions with iodine deficiency, as well as their association with thyroid function, body mass index (BMI), glucose and HbA1c levels, thyroid volume, and urinary iodine concentration. The study was conducted in the Muynak, Takhtakupyr, and Kanlykul districts of the Republic of Karakalpakstan and included 733 participants over 40 years of age. Based on laboratory and instrumental findings, statistically significant positive correlations were identified between TSH levels and parameters of carbohydrate metabolism. The obtained data indicate a pathogenetic link between iodine deficiency and the development of metabolic disorders. Keywords: iodine deficiency, prediabetes, diabetes mellitus, thyroid gland, TSH, BMI, glucose, metabolic syndrome. Introduction. Iodine deficiency in endemic regions may be associated not only with impaired thyroid function and endocrine disorders, but also with metabolic syndrome and disturbances in carbohydrate metabolism. According to WHO data, about 2 billion people worldwide suffer from iodine deficiency. Iodine deficiency negatively affects not only thyroid function but also overall metabolism, including insulin sensitivity and glucose utilization (Zimmermann, 2009). In recent years, monitoring studies have also been conducted in our country, particularly focusing on the prevalence of metabolic disorders such as prediabetes and type 2 diabetes mellitus in iodinedeficient regions. Over the past decades, a global increase in endocrine disorders has been observed, especially type 2 diabetes mellitus (T2DM) and thyroid dysfunction. According to WHO data, the number of people with diabetes reached more than 537 million in 2021, and it is projected to rise to 783 million by 2045 [1]. Prediabetes is also considered a global problem, as it is a direct risk factor for the development of T2DM and often progresses asymptomatically. Iodine deficiency is one of the major etiological causes of endemic thyroid diseases. According to WHO estimates, more than 30% of the world’s population is affected by iodine deficiency, which contributes to a high prevalence of thyroid disorders [2]. Uzbekistan is also among the regions at risk of iodine deficiency. In the mountainous and foothill areas of the country, a significant portion of the population lives under conditions of insufficient iodine intake, which leads to thyroid dysfunction, particularly hypothyroidism and increased incidence of endemic goiter [3]. Previous studies have demonstrated a strong association between thyroid function and metabolic syndrome, insulin resistance, and diabetes mellitus. For example, in a study by Boelaert SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 56 et al., it was found that changes in thyroid hormone levels—triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH)—are closely related to metabolic parameters, including blood glucose levels [4]. It has been noted that both elevated and decreased TSH levels can affect insulin sensitivity and contribute to the development of type 2 diabetes mellitus (T2DM) [5]. The association between subclinical hypothyroidism, prediabetes, and T2DM is particularly pronounced, as demonstrated by numerous studies. In a large population-based study conducted by Lee et al., it was found that individuals with elevated TSH levels had a significantly higher prevalence of prediabetes [6]. Under conditions of iodine deficiency, inadequate synthesis of thyroid hormones may negatively affect metabolic balance by reducing glucose utilization in peripheral tissues. This, in turn, may promote the development of insulin resistance [7]. Additionally, patients with hypothyroidism experience a reduction in basal metabolic rate, which leads to increased body weight and the development of dysglycemia [8]. This article examines the prevalence of prediabetes and T2DM among populations living in iodine-deficient regions, as well as their association with thyroid function. Research in this area is essential for improving public health, early diagnosis, and the development of preventive strategies. The aim of this study is to determine the prevalence of carbohydrate metabolism disorders, particularly prediabetes and T2DM, among populations residing in regions with endemic iodine deficiency, and to assess their relationship with thyroid function, anthropometric indicators, and other metabolic markers. Materials and Methods. The study was designed as a cross-sectional epidemiological survey and was conducted in three iodine-deficient districts of the Republic of Karakalpakstan (Muynak, Takhtakupyr, and Kanlykul). The research was carried out from January to June 2025. During this period, a screening of the population in these three districts was performed. A total of 14,184 individuals aged over 40 years were examined. All participants underwent the following laboratory and instrumental assessments: • Fasting blood glucose and plasma HbA1c levels; • Thyroid function markers: TSH, free T3, and free T4; • Anthropometric measurements: body weight, height, and body mass index (BMI); • Thyroid ultrasound examination to assess its volume and structural characteristics; • Urinary iodine concentration measured using ion-selective electrodes; • A socio-demographic questionnaire including age, sex, place of residence, and occupation. Statistical analysis was performed using SPSS version 26.0. Quantitative variables were presented as M ± SD. Between-group comparisons were conducted using Student’s t-test, ANOVA, and Spearman’s and Pearson’s correlation analyses. A p-value < 0.05 was considered statistically significant. Results of the Study. The primary objective of the study was to determine the prevalence of carbohydrate metabolism disorders in an iodine-deficient population and to identify their association with thyroid function and anthropometric indicators. Among the 14,184 individuals examined, a total of 733 patients met the inclusion criteria (prediabetes, type 2 diabetes mellitus, or obesity in combination with iodine deficiency, normal thyroid function, and absence of severe somatic diseases). The distribution of these conditions was as follows: SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 57 1. Patients with prediabetes associated with iodine deficiency – 297 individuals (41%). 2. Patients with prediabetes and normal thyroid function – 150 individuals (20.5%). 3. Patients with type 2 diabetes mellitus associated with iodine deficiency – 86 individuals (11.7%). 4. Patients with type 2 diabetes mellitus and normal thyroid function – 50 individuals (6.8%). 5. Patients with obesity associated with iodine deficiency – 107 individuals (14.6%). 6. Patients with obesity and normal thyroid function despite iodine deficiency – 43 individuals (5.9%). The findings demonstrated a strong association between iodine deficiency and the prevalence of prediabetes, type 2 diabetes mellitus, and obesity. These results confirm the clinical significance of monitoring thyroid function and iodine status in patients with metabolic disorders, as well as the need for targeted prevention strategies in iodine-deficient regions. Table 1. Screening results in iodine-deficient regions Region Population % Age 40+ Screened Prediabetes % Type 2 Diabetes % Obesity % Muynak 28 097 8 337 3 620 82 (2,26%) 34 (0,9%) 76 (2%) Takhtakupyr 37 566 11 445 4 614 141 (3%) 43 (0,93%) 38 (0,8%) Kanlykul 53 796 15 280 5 950 224 (3,76%) 59 (0,9%) 36 (0,9%) As shown in Table 1, a high prevalence of carbohydrate metabolism disorders associated with iodine deficiency was observed in all surveyed regions. Particular attention should be paid to the Kanlykul district, where the prevalence of prediabetes significantly exceeds that of other districts, highlighting the need for targeted preventive measures in this region. Table 2. Mean values by groups (M ± SD) Parameter Prediabetes Group Type 2 Diabetes Group Obesity Group Glucose (mmol/L) 6.2 ± 0.5 8.3 ± 0.7 5.1 ± 0.3 HbA1c (%) 6.1 ± 0.4 8.9 ± 0.8 5.4 ± 0.2 BMI (kg/m²) 27.3 ± 3.2 29.7 ± 4.1 24.5 ± 2.5 TSH (µIU/mL) 5.3 ± 1.1 6.7 ± 1.5 2.2 ± 0.6 The obtained results indicate a strong association between carbohydrate metabolism disorders and thyroid function in the context of iodine deficiency. The most pronounced changes were observed in the diabetes group, where glucose and HbA1c levels were significantly elevated. An increase in body mass index (BMI) also suggests that iodine deficiency is accompanied by the development of metabolic syndrome. Table 2. Table 3. Correlation analysis (r values) SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 58 Indicator Pair Indicator Pair Indicator Pair TSH vs Glucose 0.64 <0.01 TSH vs HbA1c 0.59 <0.01 BMI vs HbA1c 0.47 <0.05 The results of the correlation analysis demonstrated a positive association between TSH levels and both glucose and HbA1c. This indicates that reduced thyroid function due to iodine deficiency may impair glucose utilization. Table 3. Table 4. Thyroid volume (ultrasound data) by groups Group Thyroid Volume (cm³) Normal Thyroid Volume Enlarged Thyroid Volume Prediabetes 12.5 ± 2.1 150 297 Type 2 Diabetes 14.7 ± 2.4 50 86 Obesity 10.3 ± 1.9 43 107 Normally, thyroid volume does not exceed 18 cm³ in women and 25 cm³ in men. An increase in thyroid volume, particularly pronounced in the diabetes group (14.7 ± 2.4 cm³), may indicate compensatory hyperplasia due to iodine deficiency. Thyroid enlargement can be considered a compensatory response to iodine deficiency. The highest thyroid volume was observed in the diabetes group, reflecting the severity of iodine deficiency and the extent of endocrine dysfunction. Table 4. Table 5. Mean iodine concentration (in 24-hour urine) Group Iodine Level (µg/L) Prediabetes 84 ± 12 Type 2 Diabetes 71 ± 15 Obesity 96 ± 10 The iodine concentration in all groups was below the minimum level established by the WHO, with the markedly reduced concentration in the diabetes group being particularly concerning. Table 5. This indicates the potential for more severe endocrine disorders in the context of iodine deficiency. Discussion. The results of this study demonstrated that in iodine-deficient regions, the prevalence of carbohydrate metabolism disorders, particularly prediabetes and type 2 diabetes mellitus (T2DM), is significantly higher. Elevated TSH levels, increased thyroid volume, and reduced urinary iodine concentration indicate that thyroid dysfunction underlies the pathophysiology of these disorders. Glucose utilization and insulin sensitivity are processes sensitive to thyroid hormone levels. Iodine deficiency disrupts this regulatory mechanism. Furthermore, increased BMI and the development of obesity may be explained by dysregulation of the hypothalamic-pituitary-thyroid axis in the context of iodine deficiency. Based on the screening data and statistical analysis, it can be concluded that iodine deficiency in our country is not only an endemic problem but also an important factor in the development of metabolic syndrome. This emphasizes the need for a comprehensive approach from the healthcare system. Conclusions. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 59 The conducted study demonstrated a high risk of developing carbohydrate metabolism disorders, particularly prediabetes and type 2 diabetes mellitus (T2DM), in the context of iodine deficiency. Reduced thyroid function, decreased iodine levels, and increased BMI were identified as key biomarkers of these conditions. A clear association between iodine deficiency and disturbances in carbohydrate metabolism was also established, supported by clinical and epidemiological data. These conditions have a significant impact on public health. Therefore, prevention of iodine deficiency, regular screening, and monitoring of thyroid function should become a priority for the healthcare system. Recommendations Encourage regular consumption of iodized products in regions with iodine deficiency. Conduct regular glycemic screenings among the population over 40 years of age. Implement thyroid function monitoring in practice, including TSH and iodine level assessment. Establish a multi-level system for diagnosis and follow-up involving endocrinologists and general practitioners. REFERENCES 1. International Diabetes Federation. IDF Diabetes Atlas, 10th ed. Brussels, Belgium: 2021. 2. World Health Organization. Iodine deficiency in Europe: A continuing public health problem. Geneva: WHO; 2007. 3. Қаюмов Ж.А., Юсупова З.А. Эндемик зобнинг эпидемиологияси ва профилактикаси. – Тошкент: Илм, 2019. 4. Boelaert K., et al. Thyroid dysfunction and metabolic syndrome. Eur J Endocrinol. 2011;164(1):1–9. 5. Maratou E., et al. Studies of insulin resistance in patients with clinical and subclinical hypothyroidism. Eur J Endocrinol. 2009;160(5):785–790. 6. Lee Y.J., et al. The relationship between thyroid function and prevalence of prediabetes and diabetes in the Korean population. J Korean Med Sci. 2018;33(3):e10. 7. Zimmermann M.B. 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