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Iron deficiency anaemia in childhood and thyroid function
Prasong Tienboon1, Kewalee Unachak
1Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand. prasong@chiangmai.ac.th
Insights
Iron deficiency anaemia in young children does not significantly alter thyroid function, preserving normal thyroid hormone levels. However, minor hypothalamic-pituitary abnormalities were observed, suggesting hypothyroidism is unlikely to cause developmental issues.
Area of Science:
- Pediatric Endocrinology
- Hematology
- Nutritional Science
Background:
- Iron deficiency anaemia (IDA) is linked to thyroid hormone metabolism changes in adults and animals.
- The impact of IDA on thyroid function in young children requires further investigation.
Purpose of the Study:
- To assess the effect of iron deficiency anaemia on thyroid function in young children.
- To compare thyroid function in anaemic children before and after iron treatment with iron-sufficient controls.
Main Methods:
- Measured thyroxine (T4), triiodothyronine (T3), free hormones (fT4, fT3), thyroxine binding globulin (TBG), and thyroid stimulating hormone (TSH) in 9 children with IDA and 8 controls.
- Assessed basal and thyrotropin releasing hormone (TRH)-stimulated thyroid hormone levels.
- Compared pre- and post-treatment IDA children with controls.
Main Results:
- Basal thyroid hormone and TBG levels were similar between IDA and control children.
- No significant differences in thyroid hormones were observed in IDA children before and after iron therapy.
- TSH response to TRH was lower in IDA children, but not statistically significant; minor hypothalamic-pituitary abnormalities were noted in 3/9 children.
Conclusions:
- Normal thyroid function is generally preserved in young children with iron deficiency anaemia.
- Hypothyroidism is unlikely to be a primary cause of impaired psychomotor development or growth in children with IDA.
Abstract:
Studies in animals and adults have indicated iron deficiency anaemia to be associated with altered thyroid hormone metabolism. The aim of the present study was to determine the effect of iron deficiency anaemia on the thyroid function of young children. Concentrations of thyroxine (T4) and triiodothyronine (T3), free thyroid hormones (fT4 and fT3), thyroxine binding globulin (TBG), and thyroid stimulating hormone (TSH) were measured in the basal state and in response to an intravenous bolus of thyrotropin releasing hormone (TRH) in nine children one to three years of age with iron deficiency anaemia (IDA) before and after treatment with oral iron. The results of the anaemic children were also compared to basal and stimulated concentrations of thyroid hormones, TBG, and TSH of eight iron sufficient, age-matched children. Seven of the IDA and 6 of the control children were male. The mean haemoglobin (Hb) and serum ferritin (SF) in the IDA children at baseline were 93g/L (range 81-102) and 6g/L (range 1-12) which increased to 121g/L (range 114-129) and 54g/L (range 19-175), respectively, after a mean of 2.3 months (SD 0.5) of iron therapy. In the control group, mean Hb and SF were 125g/L (range 114-130) and 51 g/L (range 24-144), respectively. The basal values of TBG and thyroid hormones of the IDA children before and after iron treatment were not different from the control children. Similarly, there was no statistical difference in the thyroid hormones in the IDA children before compared to after resolution of the anaemia. Compared to the control children, the TSH response over time to TRH, TSH area under the curve (TSHAUC), and the peak TSH value after stimulation were all lower in the IDA children both before and after resolution of anaemia, but the differences were not significant. Iron therapy and resolution of anaemia had no effect among the IDA children. The time to reach the peak TSH concentration was longer in the IDA children (P=0.08) than the control children before iron therapy. While the time to peak TSH decreased upon resolution of the anaemia, the difference was not significant. There was no effect of Hb concentration, age, or anthropometry with TSH, TSHAUC, or time to peak TSH after TRH stimulation in the IDA children before treatment. Normal thyroid function was preserved in these children with iron deficiency anaemia, however three of nine children had minor abnormalities of hypothalamic-pituitary function. These results indicate that hypothyroidism is unlikely to be a major cause of impaired psychomotor development or growth in young children with iron deficiency anaemia.