|Year : 2016 | Volume
| Issue : 1 | Page : 41-44
Nutritional iodine status of pregnant women in Zaria, North-Western Nigeria
Mohammed El-Bashir Jibril1, Fayeofori M Abbiyesuku2, IS Aliyu1, AJ Randawa3, R Adamu1, SA Akuyam1, M Manu1, HM Suleiman1, S Adamu4, R Yusuf1, A Mohammed1
1 Department of Chemical Pathology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
2 Department of Chemical Pathology, University College Hospital, Ibadan, Nigeria
3 Department of Obstetrics and Gynaecology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
4 Department of Chemical Pathology, Federal Teaching Hospital, Gombe, Nigeria
|Date of Submission||19-May-2015|
|Date of Acceptance||26-Aug-2015|
|Date of Web Publication||12-Feb-2016|
Mohammed El-Bashir Jibril
Department of Chemical Pathology, Ahmadu Bello University Teaching Hospital, Zaria
Background: Iodine deficiency is a major public health problem worldwide, especially in pregnant women and young children. It is the most common cause of preventable mental retardation all over the world. Few among the devastating outcomes of iodine deficiency in pregnancy are increased perinatal mortality, abortions, stillbirths, neonatal hypothyroidism, goiter, and congenital anomalies. Objective: To assess the nutritional iodine status of pregnant women in Zaria. Methods: Four hundred subjects were recruited for this study consisting of three hundred apparently healthy pregnant women and one hundred apparently healthy nonpregnant age-matched controls. Random urine samples were collected and analyzed for iodine by modified Sandell-Kolthoff reaction. Data were analyzed using Epi-Info 3.5.3 to obtain the mean ages and median urinary iodine concentration (UIC) for pregnant women, controls and then for each trimester of pregnancy. P ≤ 0.05 was considered statistically significant. Results: Mean ages ± standard deviation for pregnant women and controls were 25.41 ± 5.98 and 26.70 ± 5.83 years, respectively (P > 0.05). Median UIC for pregnant women and controls were 193 μg/L and 205 μg/L, respectively. Trimester-specific UICs were 250 μg/L, 154 μg/L, and 150 μg/L for the first, second, and third trimesters, respectively. The percentage of women with iodine deficiency increased with advancing gestational age. Conclusion: Pregnant women in Zaria were iodine sufficient. There was a progressive decline in median UIC from the first through the third trimester.
Keywords: Iodine, nutrition, pregnancy, thyroid, trimester
|How to cite this article:|
Jibril ME, Abbiyesuku FM, Aliyu I S, Randawa A J, Adamu R, Akuyam S A, Manu M, Suleiman H M, Adamu S, Yusuf R, Mohammed A. Nutritional iodine status of pregnant women in Zaria, North-Western Nigeria. Sub-Saharan Afr J Med 2016;3:41-4
|How to cite this URL:|
Jibril ME, Abbiyesuku FM, Aliyu I S, Randawa A J, Adamu R, Akuyam S A, Manu M, Suleiman H M, Adamu S, Yusuf R, Mohammed A. Nutritional iodine status of pregnant women in Zaria, North-Western Nigeria. Sub-Saharan Afr J Med [serial online] 2016 [cited 2019 Oct 16];3:41-4. Available from: http://www.ssajm.org/text.asp?2016/3/1/41/176312
| Introduction|| |
Iodine is a micronutrient necessary for the synthesis of thyroid hormones that play decisive roles in many metabolic processes especially the development and maturation of central nervous system. ,, Impairment of nervous system development, miscarriages, stillbirth, small for date, preterm delivery, cretinism, and postpartum hemorrhage are few among the effects of iodine and thyroid hormone deficiency in pregnancy  termed "iodine deficiency disorder (IDD)." The term IDD refers to all the ill-effects of iodine deficiency in a population, that can be prevented by ensuring that the population has adequate intake of iodine.  IDDs are primarily the result of the inadequate amount of iodine in the soil, water, and food as well as consumption of food rich in goitrogenic substances. ,
Several parts of Nigeria were identified with goiter endemicity and labeled goiter belt. Goiter belt in Nigeria was described in 1954 where the distribution of goiter was explained on a basis of geology.  In granite areas of Northern Nigeria, food was of poor quality, and there was little iodine in water and soil. Some villages in the goiter belt had goiter rates as high as 60% and higher prevalence of cretinism when compared with central plateau and marine areas where the soil and water were rich in iodine.  There was no evidence of other goitrogenic factors apart from iodine deficiency in the country. 
Several indicators are usually utilized in the assessment of iodine status of a population namely: Thyroid size by palpation or ultrasonography, urinary iodine concentration (UIC), thyroid stimulating hormone, and thyroglobulin measurements in blood. Iodine excretion from spot urine samples has been widely accepted as a satisfactory index of iodine intake.  Median UIC was recommended by World Health Organization to classify countries into different degrees of public health significance. Pregnant women with median UIC below 150, 150-249, 250-500 and above 500 μg/L are considered inadequate, adequate, more than adequate, and excessive, respectively.  In nonpregnant population, UIC of 100-199 μg/L is considered adequate while mild iodine deficiency is represented by UIC of 50-99 μg/L. 
In 1993 national goiter rate in Nigeria was 20% and 20 million Nigerians were estimated to be affected by IDD.  Prevalence of iodine deficiency was 65.6% in South East, 41% in South West and 43% in North Western Nigeria.  As part of the strategies to reduce the prevalence of IDD in Nigeria, universal salt iodization (USI) program was introduced in 1995.  To ensure effective iodization and iodine sufficiency among Nigerian population, the federal government passed an act in 2001 mandating the iodization of all edible or table salts. By 2003, the national household coverage of iodized salt was 97.3% and Nigeria was the first African country declared iodine sufficient in 2007.  Soon after that, the level of salt iodization dropped to < 75%. 
| Materials and Methods|| |
The study involved 300 pregnant women (75 in the first trimester, 125 in the second trimester, and 100 in the third trimester) and 100 nonpregnant controls. The pregnant subjects were recruited from the antenatal clinics of Ahmadu Bello University Teaching Hospital, Ahmadu Bello University Sickbay, Hajia Gambo Sawaba Hospital, and PHC Audu Kwari Sabon Gari, Zaria while the controls were recruited from the township community. The ages of the participants ranged between 14 and 45 years. All subjects were apparently healthy with no evidence of renal, hepatic, endocrine, or other metabolic diseases that would affect thyroid function. None of the participants was on the restricted salt intake or smokes a cigarette. They were also not on iodine supplement or any drug that may affect thyroid function or iodine metabolism. Each subject had resided in the locality for at least 1 year before the study. Ethical approval was obtained from Kaduna State Ministry of Health and informed written consent was obtained from the subjects. Urine samples (5-10 ml) were collected between 9 and 11 am (when urinary iodine was lowest)  and were frozen at -20°C until analysis. A structured questionnaire was used to collect demographic data and sources of iodine or goitrogen from the subjects. Consumption of frozen or smoked sea fish of at least twice weekly was considered "regular intake" while consumption of cabbage or cassava products (common goitrogens in the area) of at least twice weekly were also considered "regular intake." UIC was measured by the modified Sandell-Kolthoff method. Statistical analysis was done using Epi-Info 3.5.3 software from Centre for Disease Control and Prevention Atlanta. Statistical significance was defined as P < 0.05.
| Results|| |
The mean ± standard deviation (SD) ages and parities of the control subjects and pregnant women were similar as seen in [Table 1]. The mean ± SD systolic and diastolic blood pressures were within normal limits but were significantly higher among the control subjects.
Seventy-eight percent of controls and 88% of the pregnant women use factory packaged salts as sources of their table salt and over 90% of all the participants admitted regular seafood intake. Regular consumption of cabbage (a goitrogen) was claimed by 88% of controls and 79% of pregnant women while that of cassava (another goitrogen) was claimed by 75% and 86% among controls and pregnant women, respectively.
As shown in [Table 2], the median UICs were 205 and 193 μg/L for the control subjects and pregnant women, respectively. Median UICs were 250, 154, and 150 μg/L among pregnant women in first, second, and third trimesters, respectively. Forty-four percent of the controls and 46% of pregnant women had UIC of <150 μg/L. Distribution of pregnant women with UIC <150 μg/L increased from 36% in the first trimester to 48.8% in the second trimester and 49% in the third trimester.
|Table 2: Distribution of nutritional iodine status across the three trimesters|
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[Table 3] shows the relationship between parity and iodine status of the subjects. Multiparous pregnant women constituted majority of the participants and was the only group among both pregnant women and controls with median UIC below 150 μg/L.
|Table 3: Distribution of nutritional iodine status by parity among controls and pregnant subjects|
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| Discussion|| |
The current study confirmed iodine sufficiency in both pregnant women and controls in Zaria. Consumption of iodized salt and seafood might have contributed significantly in achieving iodine sufficiency in this environment. This agrees with several reports that Nigeria is iodine sufficient country ,,,,, but contrary to a finding of mild iodine deficiency in pregnant women in Abia state of Nigeria, which was attributed to excessive cassava intake (a goitrogen), the major staple food in the area.  Consumption of goitrogens such as cassava and cabbage were common in Zaria, but iodine sufficiency was maintained probably due to high consumption of factory packaged salt and seafood. In addition to that, the soil and water sources of Zaria are likely to be iodine rich since it was not mentioned as part of Nigerian goiter belt in 1954. Another study reported that the total number of operations performed for thyroid diseases in ABU Teaching Hospital had reduced, and that of thyrotoxicosis had tripled over 10 years period from 1986 to 1995 affecting mainly the young and was attributed to USI to combat goiter. 
Iodine level was higher among the control subjects when compared with pregnant subjects because of increased demand for iodine in pregnancy. There was also a decrease in median UIC with an increase in gestational age. The highest value was seen in first trimester followed by a sharp decline in second trimester which was slightly higher than third-trimester level. The percentage of pregnant women with iodine deficiency (UIC <150 μg/L) increased with advancing gestational age. This pattern was similar to the ones obtained elsewhere. , This could be explained by the passage of iodine from maternal circulation to foeto-placental unit. By the end of the first trimester to middle of the second trimester, fetal thyroid gland was ready to commence thyroid hormone synthesis.  Another possibility increases in renal clearance and iodine uptake by thyroid gland during pregnancy. The average thyroid clearance rate for iodide is 17 ml/min and is said to be increased in pregnancy.  The renal iodide clearance is 30 ml/min, resulting mainly from glomerular filtration with no evidence of tubular secretion or active transport. During pregnancy, the renal clearance of iodide increase significantly because of increased glomerular filtration rate which begins in the early weeks of pregnancy and persists till term referred to as an "obligatory renal iodine leakage."  This reaches up to 60 ml/min and accompanied by an absolute elevation of iodide entry into the gland thereby decreasing the nutritional iodine status of the pregnant population. 
There was no specific pattern of urinary iodine levels with parity. Only multiparous women in both pregnant and control groups had an iodine deficiency. This is consistent with the finding that urinary iodine excretion does not correlate with parity or gravidity. 
| Conclusion|| |
Nutritional iodine status of women in Zaria was adequate. Government efforts through 1995 USI program, subsequent national assembly bill of 2001 mandating iodization of all table salts in the country and high seafood intake in the environment might have played important roles in achieving this.
Financial Support and Sponsorship
Conflicts of Interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]