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Recombinant Thyrotropin in the Diagnosis of Congenital Hypothyroidism

Division of Endocrinology (D.T., Z.H.), Meyer Children’s Hospital, and Endocrine Laboratory (Z.S.O.), Rambam Medical Center, Haifa 31096, Israel; Department of Pediatrics (L.E.), Nahariya Hospital, Nahariya 22100, Israel; and Technion-Israel Institute of Technology (L.E., Z.H.), Haifa 32000, Israel

Address all correspondence and requests for reprints to: Dov Tiosano, Meyer Children’s Hospital, POB 6092, Haifa 31096, Israel. E-mail: d_tiosano{at}rambam.health.gov.il.

Context: A modern approach to congenital hypothyroidism requires a definitive diagnosis of the underlying mechanisms; this can be achieved within the first weeks of life. When uncertainty persists, treatment is commenced, and the definitive diagnosis of congenital hypothyroidism is deferred to the age of 3 yr.

Objectives: The interruption of thyroid replacement treatment is perceived as risky by parents and physicians. The aim of this pilot study was to test the possibility of a definitive diagnosis during thyroid replacement treatment, using stimulation of thyroid tissue by recombinant human (rh)TSH.

Subjects: Eight patients, three boys and five girls, age 5–15 yr (mean, 9.5 ± 3.7 yr), with congenital hypothyroidism that had been diagnosed by the neonatal screening program, and having their diagnosis verified between the ages of 3–4 yr, were reevaluated while on thyroid replacement therapy.

Interventions: Patients received im 0.6 mg/m² rhTSH on two consecutive days.

Results: rhTSH pharmacokinetics, maximal concentration, t_1/2, and area under the curve in children were different as compared with adults. In the patients with intact TSH receptors, free T₄ levels decreased after the first and the second injection of rhTSH (P = 0.0137 and P = 0.0149, respectively). All eight children showed identical scintigraphy after rhTSH administration as compared with thyroid replacement withdrawal.

Conclusions: The use of rhTSH is effective for definitive diagnosis of congenital hypothyroidism during thyroid replacement treatment, and no safety issues were encountered.