بررسي ميانگين حجم تيروييد افراد نرمال توسط سونوگرافي و ارتباط آن با سن ، جنس و وزن بدن در افراد سالم شهر اصفهان

DETERMINATION OF THE MEAN THYROID VOLUME IN NORMAL POPULATION USING ULTRASONOGRAPHY AND ITS CORELATON WITH AGE , SEX AND BODY WEIGHT

Thyroid enlargement is one of the most common diseases in our country . It is therefore necessary to define the size of the normal gland in any region and then to undestand the effects of physiologic factors on thyroid size. The size of the gland can be affected by some factors including genetic, environmental and geographic factors, including daily iodine intake. The purpose of this study was the measurement of mean thyroid volume in normal subjects and determination of relationship between thyroid volume and physiologic factors including sex, age and body weight. This study was s cross sectional, descriptive, analytical study, which was performed during one year (1999 - 2000) in Isfahan, Iran. The target population was 247 normal cases aged between 18 - 65 years , who were referred from the internal medicine clinic to the sonographic department. At first , these subjects were examined by an endocrinologist and patients with clinical goiter, other thyroid diseases, severe diseases, pregnancy and users of certain drugs were excluded from the study. Then the diameters of their thyroid glands were measured by ultrasound equipment (Dornier) using 5 and 7.5 MHz transducers and the thyroid volume was calculated by using the formula: dl d2 d3 0.479 = V (ml). The data was analyzed by SPSS and the results were obtained by T test and variance analysis. The mean thyroid volume in the target population was 7.97+3.38 ml. The mean thyroid volume in men (8.91+ 3.48 ml) was greater than the mean thyroid volume in women (7.16 ± 3.08 ml) with P < 0.0001. Also , the ratio of thyroid volume to body weight was calculated in men (0.124 0.04) and women (0.111 ± 0.04) [p-0.04]. Results showed that thyroid volume increases with age (P <0.014) and body weight (P<0.001). According to these results, the mean thyroid volume in this study was less than the mean thyroid volume in other similar studies. The difference in body habitus and lean body mass could have a significant role in this case. Mean thyroid volume was greater in men as compared to women, which is essentially due to the difference in body weight and mass between men and women. Also, the increase in thyroid volume with increase in age and body weight is compatible with the results of other studies.