Endocrine Abstracts

Objective: Croatia is iodine sufficient country due to universal salt iodization as documented by epidemiological studies with urinary iodine measurement in schoolchildren and pregnant women, as well as women of reproductive age. However, high salt intake is present and program for reduction of salt intake in Croatia is initiated. The epidemiological project funded by Croatian science foundation EHUH2 was carried out to investigate prevalence of hypertension and related risk factors, salt intake as well as iodine intake and thyroid diseases in the population. The aim of the study was to assess iodine and salt intake and thyroid diseases in adult population from different regions of Croatia. SUBJECTS: The study enrolled 1146 adult subjects (819 females and 327 males), median age 58 (18-90) years.

Methods: Questionnaire, serum and 24-hour urine samples were collected for thyroid function tests and urinary iodine (UIC), sodium and creatinine measurement. All subjects underwent thyroid ultrasound (US) (GE Healthcare Logiq eR7 device with 12 MHz linear transducer) for assessment of thyroid volume and nodularity. UIC was measured by modified Sandel-Kolthoff method using microtiter plate technique.

Results: There were 115 (10.0%) (100 female and 15 male) subjects on L-T4 therapy due to hypothyroidism, 5 (0.4%) subjects on methimazole therapy due to hyperthyroidism. A total of 13 (1.1%) subjects underwent thyroid surgery due to benign thyroid conditions, and 8 (0.7%) subjects due to differentiated thyroid cancer. Ectopic sublingual thyroid was recorded in one subject. Thyroid nodules were detected in 550 (48.0%) subjects: 117 (21.3%) males and 433 (78.7%) females, with increasing prevalence with age and highest prevalence in rural areas with elderly population. An overall median UIC in adult population of Croatia was 131.1 µg/l. There were 29.3% of samples with UIC < 100 µg/l, 66.7% of samples between 100-300 µg/l, and 4.0% of samples with UIC > 300 µg/l. Furthermore, there was no difference in UIC medians between males and females and no significant difference between coastal and continental regions of Croatia (UIC medians around 130 µg/l). CONCLUSIONS: Present study confirms sufficient iodine intake in adult subjects in all investigated areas of Croatia according to medians of UIC. Interestingly, similar median UIC around 130 µg/l was recorded in most regions, with no difference between males and females. High prevalence of thyroid nodules and hypothyroidism on L-thyroxine therapy was recorded in female subjects in all geographical regions. The highest prevalence of thyroid nodules was recorded in rural areas with predominantly elderly female population.