Clinical course of congenital hypothyroidism with gland in situ and necessity of L-thyroxine therapy after re-evaluation.

Context: Clinical course and need for long-term L-thyroxine (LT4) therapy of congenital hypothyroidism (CH) with gland in situ (GIS) remain unclear.

Objective: To describe the clinical history of CH with GIS and evaluate the proportion of patients who can suspend therapy during follow-up.

Design and setting: Retrospective evaluation of patients followed at referral regional center for CH of Pisa.

Patients: 77 patients with confirmed primary CH and GIS after positive neonatal screening were included. All children started LT4 at CH confirm.

Interventions: At 3 years of age, 55 children underwent a clinical re-evaluation after withdrawal of therapy with hormonal examinations, imaging of the thyroid gland with ultrasonography and 123-iodine with perchlorate discharge test. Subsequent periodic controls of thyroid function were executed and, when possible, a new attempt to stop LT4 was performed. Adequate follow-up data (at least 6 months after treatment suspension trial) were available for 49 patients.

Results: Among the 55 patients who were reassessed, 18 (32.7%) were euthyroid. Considering subsequent follow-up, 49% of patients were no longer treated and 51% were taking therapy. No differences in neonatal parameters were observed between the two groups; LT4 dose before the last trial off medication was higher in permanent CH (p 0.016).

Conclusion: Monitoring of thyroid function in children with CH and GIS is necessary to evaluate the need for substitution and avoid overtreatment. Even if therapy can be suspended, patients need to be monitored because apparently normal thyroid function may decline several months after withdrawal of LT4.