High Thyroid-stimulating Hormone Level in Down's Syndrome: A Mere Resetting of Hypothalamopituitary Axis in Subclinical Hypothyroidism?

OBJECTIVE: Hyperthyrotropinemia (HT) or reduced thyroid function in Down syndrome (DS) is not uncommon, causes range from glandular dysgenesis to altered hypothalamopituitary axis. In the present study, we have compared hypothyroid Indian children with and without DS (NDS), especially focusing on family history, goiter, and biochemical features. METHODS: We conducted this retrospective observational study from previous medical records of children with DS (1-17 years) having an elevated TSH (≥5 mIU/L) who were consecutively referred for with HT to Endocrinology OPD of a tertiary care hospital in India. Records from hypothyroid children (1-17 years) without Down Syndrome (NDS) were evaluated as controls. Free thyroxine (FT4), anti-thyroid peroxidase (TPO) antibody were measured and congenital hypothyroidism was excluded in all subjects. RESULTS: Thirty-four DS cases [median age 8 years (IQR: 2-14), M: F = 13:21] and 34 controls [median age 10.5 years (IQR: 7-13.25), M: F = 13:21] were comparable in terms of age and sex, Median age of presentation was significantly earlier in case of DS vs NDS [7 years vs. 10 years]. DS children had significantly less family history of thyroid disorders compared to NDS [14.7% vs 64.7%]. Goiter was significantly less common in patients with DS [DS - 32.25% vs. NDS - 73.5%, P = 0.001]. Anti-TPO antibody positivity was significantly less common in patients with DS [DS- 41% vs. NDS- 73.5%, P = 0.014]. CONCLUSION: There is a significant difference in presentation in hypothyroid children with DS compared to NDS. DS children with hypothyroidism compared to NDS, had earlier presentation, lower incidence of traceable family history, goiter, and anti-TPO-antibody positivity.