A hospital based prospective observational study was conducted with 66 children to assess the prevalence of abnormal thyroid functions in children with chronic kidney disease and to correlate abnormal thyroid functions with different etiologies of chronic kidney disease and different stages of chronic kidney disease.
Distribution of children as per Thyroid Function Test Results
28 out of 66 children had thyroid disorders. The prevalence of thyroid disorders in our study was 42.4%. The prevalence of subclinical hypothyroidism and hypothyroidism was 33.3% and 9.1% respectively (Table & graph 1).
Distribution of children according to Age
The mean age of children with subclinical hypothyroid and hypothyroid was 6.95 ± 2.94 years and 6.83 ± 3.82 years respectively while the mean age of euthyroid children was 6.97 ± 3.21 years. There was no significant difference between the groups as per ANOVA test (p>0.05)(table & graph 2).
Distribution of children according to Sex
16 (72.7%) and 6 (27.3%) children with subclinical hypothyroid were male and female respectively while 4 (66.7%) and 2 (33.3%) children with hypothyroid were male and female respectively. 27 (71.1%) and 11 (28.9%) euthyroid children were male and female respectively. There was no significant difference between the groups as per Chi-Square test (p>0.05) (table & graph 3).
Anthropometry measurements of children
The mean height of children with subclinical hypothyroid and hypothyroid was 105.95 ± 15.19 cms and 102.17 ± 24.01 cms respectively while the mean height of euthyroid children was 105.47 ± 16.28 cms. The mean weight of children with subclinical hypothyroid and hypothyroid was 16.41 ± 6.27 kgs and 15.02 ± 6.29 kgs respectively while the mean weight of euthyroid children was 16.58 ± 6.59 kgs. There was no significant difference between the groups as per ANOVA test (p>0.05) (table & graph 4).
Distribution of children according to Age of Onset of Disease
The mean age of onset of disease of children with subclinical hypothyroid and hypothyroid was 3.71 ± 2.5 years and 4.38 ± 3.90 years respectively while the mean age of onset of disease of euthyroid children was 3.69 ± 2.55 years. There was no significant difference between the groups as per ANOVA test (p>0.05) (table & graph 5).
Distribution of children according to Family History of Thyroid Dysfunction
No child with subclinical hypothyroid and hypothyroid had family history of thyroid dysfunction while 2 (5.3%) euthyroid children had family history of thyroid dysfunction. There was no significant difference between the groups as per Chi-Square test (p>0.05) (table & graph 6).
Distribution of children according to Clinical Presentation
1 (4.5%) and 2 (9.1%) children with subclinical hypothyroid had constipation and sensitivity to cold / dry skin respectively while 1 (16.7%) child with hypothyroid had sensitivity to cold / dry skin. 2 (5.3%) and 3 (7.9%) euthyroid children had constipation and sensitivity to cold / dry skin respectively. There was no significant difference between the groups as per Chi-Square test (p>0.05) (table & graph 7).
Distribution of children according to Treatment History
17 (77.3%) and 18 (81.8%) children with subclinical hypothyroid were prescribed anti HTN and EPO injection respectively while 21 (95.4%) and 22 (100%) children were on iron and calcium supplementation respectively. 5 (83.3%) and 6 (100%) children with hypothyroid were prescribed anti HTN and EPO injection respectively while 5 (83.3%) and 6 (100%) children were on iron and calcium supplementation respectively.
30 (78.9%) and 31 (81.6%) euthyroid children were prescribed anti HTN and EPO injection respectively while 36 (94.7%) and 38 (100%) children were on iron and calcium supplementation respectively. There was no significant difference between the groups as per Chi-Square test (p>0.05) (table & graph 8).
Distribution of children according to Proteinuric CKD
4 (18.2%) and 1 (16.7%) child with subclinical hypothyroid and hypothyroid respectively had proteinuric CKD while 10 (26.3%) euthyroid children had proteinuric CKD. There was no significant difference between the groups as per Chi-Square test (p>0.05) (table & graph 9).
Distribution of children according to Biochemical parameters
The mean BUN, creatinine and eGFR values of children with subclinical hypothyroid were 46.14±18.53mg/dL, 3.27±2.27mg/dL and 21.14±12.19 ml/min/1.73m2 respectively. The mean BUN, creatinine and eGFR values of children with hypothyroid were 38.67±15.54mg/dL, 4.88±1.92mg/dL and 22.08±21.05 ml/min/1.73m2 respectively.
The mean BUN, creatinine and eGFR values of euthyroid children were 48.45±19.81mg/dL, 3.43±2.46mg/dL and 21.74±12.46 ml/min/1.73m2 respectively. There was no significant difference between the groups as per Chi-Square test (p>0.05) (table & graph 10).
Correlation of CKD Stage with Thyroid function of children
3 (13.6%) and 10 (45.5%) children with subclinical hypothyroid had Stage 3 and Stage 4 CKD respectively while 9 (40.9%) children had Stage 5 CKD. 2 (33.3%) and 4 (66.7%) children with hypothyroid had Stage 3 and Stage 5 CKD respectively.
4 (10.5%) and 19 (50%) euthyroid children had Stage 3 and Stage 4 CKD respectively while 15 (39.5%) children had Stage 5 CKD. It was observed that with increasing severity of CKD, hypothyroidism also increase from 33.3% in stage 3 to 66.7% in stage 5 CKD. There was correlation of CKD Stage with thyroid function of children as per Chi-Square test (p<0.05) (table & graph 11).
Correlation of eGFR with thyroid function parameters
It was observed that with decrease in eGFR values there was significant increase in TSH values and significant decrease in FT3 values while the difference in FT4 value was comparable. There was significant correlation of eGFR with TSH and FT3 values as per ANOVA test (p<0.05) (table & graph 12).
The interplay between thyroid and the kidney in each other's functions is known for many years. Thyroid dysfunction affects renal physiology and development, whereas kidney disease could result in thyroid dysfunction. Disorders of the thyroid and kidney may co-exist with common etiological factors. In addition, treatment strategies of one disease may affect those of the other organ.
There are several interactions between thyroid and kidney functions in each other organ's disease states. Thyroid hormones affect renal development and physiology. Thyroid hormones have pre-renal and intrinsic renal effects by which they increase the renal blood flow and the glomerular filtration rate (GFR). Hypothyroidism is associated with reduced GFR and hyperthyroidism results in increased GFR as well as increased renin – angiotensin – aldosterone activation. CKD patients also have increased incidence of primary hypothyroidism and subclinical hypothyroidism.
In the present study, 28 out of 66 children had thyroid disorders. The prevalence of thyroid disorders in our study was 42.4%. The prevalence of subclinical hypothyroidism and hypothyroidism was 33.3% and 9.1% respectively. This is similar to the studies of El-Hana NA et al19 and Bajaj S et al20.