Socio demographic characteristics
Out of 698 children, 694 children were included in the analysis (response rate = 99.42%). The mean age of the study participants’ was 8.6 years (SD = 1.93). Three hundred twenty three (46.5%) children were males. Majority (93.2%) of mothers/caregivers were Orthodox Christians. Five hundred fifty nine (80.5%) of mothers/caregivers were unable to read and write and 474(68.3%) were house wives (Table 1).
This study showed that five hundred forty seven (78.8%) of mothers/caregivers usually add salt late at the end of cooking. Most (87.5%) of the mothers/caregivers did not expose salt to sunlight while 587 (84.6%) of them covered the salt containers. Among household salt samples, iodine concentration varied from 0 ppm to 30 ppm by using MBI rapid test kits. Two hundred six (29.7%) households used salt with adequate iodine level (≥15 ppm) (Table 2).
Millet and cabbage were goitrogens frequently eaten by children. Fish was also consumed by small number of children. Pond was their source of drinking water for majority (65.9%) of participants (Table 3).
Prevalence of goiter
The overall prevalence of goiter was found to be 37.6%. Prevalence of Grade 1 goiter was 28.5% and that of grade 2 was 9.1%. In terms of the WHO, UNICEF and ICCIDD criteria for assessing the severity of IDD using prevalence of goiter, the prevalence in the study area could be seen as high and IDD was severe public health problem .
This finding was in agreement with findings of a national epidemiological goiter survey among children in Ethiopia which was 39.9% (95%CI: 38.6%, 41.2%)  and in Sudan (38.8%) .
The Prevalence in the current study was higher than in studies done at South Africa (25.5%) , southern Blue Nile area of Sudan (22.3%) , India (20.5%) , Rajasthan (11.4%)  but it was lower than a study done on schoolchildren in Islamabad which was 71.6% . The Prevalence was also lower than the cross-sectional study done among ten villages from four administrative regions of Ethiopia with a gross prevalence of goiter among school children of 53.3% . The reason may be due to the fact that our study was undertaken after universal salt iodization launched in Ethiopia.
The study revealed that prevalence of goiter was 98% higher among females when compared to that of males (AOR = 1.98, 95% CI: 1.38-2.85). This may be due to the fact that iodine requirement for female children were higher than males especially at the beginning of pubertal age. This is related to the difference in sex hormones and pubertal growth pattern among boys and girls in higher age groups. This finding was similar with different studies [13, 15, 16, 20, 21] but in a study conducted at Sudan and china there were no significant difference between boys and girls [11, 14, 24].
Factors associated with goiter
For a unit increase in age, there was a 1.24 times increased risk of developing goiter in children (AOR: 1.24,95% CI: 1.12, 1.36) (Table 4). This might be due to the fact that iodine requirement increases with age. Older children had prolonged exposure for iodine deficient environment and also universal salt iodization was implemented in the past few years and older ones are less benefited from the intervention. Thyroid size is correlated with body surface area and increases with age. Hence, enlarged thyroid could be more visible and palpable in elderly children. This finding was similar with study done in Lesotho  but it was different from in china which indicated no statistically significant difference among the goiter rates across the different age groups .
Family history of goiter was significantly associated with goiter in this study. Children having goiter in first degree relative were 3.18 times more likely to develop goiter when compared with those who had no (AOR = 3.18,95% CI: 2.08,4.86) (Table 4). This finding was in agreement with a survey of goiter in Brazil  and Ethiopia . In a case control study in Germany, Patients with goiter had showed a significantly higher proportion of parents or siblings with goiter. Children from parents’ with goiter showed a 2.7 fold increased risk of developing goiter . Thus, the significantly higher rate of positive family histories of goiter in children indicates the importance of genetic factors in goiter development.
In this study the kebele where the child was living had independently associated with the development of goiter. Children who live in Workmidir kebele were 2.83 times more likely to have goiter than their counterparts in Aykuachakirn kebele (AOR = 2.83, 95% CI: 1.24, 6.48) where as children in Genbera and Worangeb kebele were 54.6% and 69.7% less likely to have goiter when compared with their counterparts in Aykuachakirn respectively ((AOR = 0.454, 95% CI: 0.207, 0.997), (AOR = 0.30, 95% CI: 0.095, 0.97)) (Table 4). Households using adequate salt iodine level in Workmidir and Aykuachakirn were low. Consumption of salt with inadequate iodine level may be the reason for increased risk of goiter in children of Aykuachakirn and Workmidir. Moreover increased consumption of fish by children in Genbera may contribute for decreased prevalence in children of this kebele.
Low dietary intakes of iodine contribute a lot for development of goiter. Hence Increasing dietary intake of iodine through consuming iodised salt is clearly the key towards eradication of goiter caused by iodine deficiency. Based on WHO recommendation salt iodine level should be adequate in 90% of households.
In Ethiopia efforts have been made to iodize the salt produced in Afdera and Dobi in Afar and Somali regions. The Federal Government of Ethiopia passed a mandatory salt regulation requiring all salt meant for human consumption to be iodized since March 2011 (33). Only 29.7% of households were using adequately iodised salt in the study area. This finding was lower than a studies done in India [12, 16], But higher when compared with a national survey in Ethiopia (15%) and Jodhpur district of Rajasthan ( 18.5%) [13, 17].
Utilization of iodised salt in the households was independently associated with development of goiter in children. Using adequately iodized salt (16–30 ppm) was protective for goiter by 55.9% than using non iodized salt (0 ppm) (AOR = 0.44, 95% CI: 0.27, 0.71). Using salt with Iodine level of 1–15 ppm was also protective for goiter by 36.6% while compared to using non iodised salt(0 ppm) (AOR = 0.63, 95% CI: 0.40, 0.99) (Table 4). This finding was similar with a study done on Qom city of Iran , But in a study on Isfaham city of Iraq there was no relationship between iodine intake and goiter .
In this study fish consumption at least once per month was 58.4% times protective for goiter than never taking fish at all (AOR = 0.42, 95% CI; 0.22, 0.80) (Table 4). Foods of marine origin have higher iodine content because marine plants and animals concentrate iodine from seawater. So sea foods including fish are naturally high in there iodine content so fish consumption will increase daily intake of iodine [4, 28].
Many studies on prevalence of goiter in Ethiopia were school based cross sectional surveys whereas the current study was community based. This study tried to include children who might not been enrolled in school or might have dropped out of school due to social stigma created by IDD. The study also differs from studies done before because it showed chronic iodine deficiency and determine recent iodine intake. The study also revealed the existence of severe iodine deficiency in the study area after Ethiopia launched universal salt iodization. But the study failed to determine the causal relationships between goiter and the predictor variables due to its cross-sectional nature. Inter observer Bias both in grading of goiter and determination of salt iodine level by rapid test kit were also limitations of this study.