Thyroid scintigraphy and perchlorate test after recombinant human TSH: a new tool for the differential diagnosis of congenital hypothyroidism during infancy.
OBJECTIVE
Prompt initiation of L-thyroxine therapy in neonates with congenital hypothyroidism (CH) often prevents the performance of functional studies. Aetiological diagnosis is thus postponed until after infancy, when the required investigations are performed after L-thyroxine withdrawal. The aim of this study was to verify the efficacy and safety of new protocols for rhTSH (Thyrogen) testing during L-thyroxine replacement in the differential diagnosis of CH.


METHODS
Ten CH patients (15-144 months old) were studied. Seven had neonatal evidence of gland in situ at the ultrasound examination performed at enrolment and received two rhTSH injections (4 microg/kg daily, i.m.) with 123I scintigraphy and perchlorate test on day 3. Three patients with an ultrasound diagnosis of thyroid dysgenesis received three rhTSH injections with 123I scintigraphy on days 3 and 4. TSH and thyroglobulin (Tg) determinations were performed on days 1, 3 and 4, and neck ultrasound on day 1.


RESULTS
rhTSH stimulation caused Tg levels to increase in eight cases. Blunted Tg responses were seen in two patients with ectopia and hypoplasia. Interestingly, in two cases the association of different developmental defects was demonstrated. Perchlorate test revealed a total iodide organification defect in two patients, including one with a neonatal diagnosis of Pendred's syndrome, who were subsequently found to harbour TPO mutations. rhTSH did not cause notable side-effects.


CONCLUSIONS
These new rhTSH protocols always resulted in accurate disease characterisation, allowing specific management and targeted genetic analyses. Thus, rhTSH represents a valid and safe alternative to L: -thyroxine withdrawal in the differential diagnosis of CH in paediatric patients.
Fugazzola
Laura
L
Department of Medical Sciences, University of Milan and Fondazione Policlinico IRCCS, Via F. Sforza, 35-20122, Milan, Italy. l.fugazzola@policlinico.mi.it
Persani
Luca
L
Vannucchi
Guia
G
Carletto
Marco
M
Mannavola
Deborah
D
Vigone
Maria Cristina
MC
Cortinovis
Francesca
F
Beccaria
Luciano
L
Longari
Virgilio
V
Weber
Giovanna
G
Beck-Peccoz
Paolo
P
D002648:Child; D002675:Child, Preschool; D003409:Congenital Hypothyroidism / Q000097:blood / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007223:Infant; D007454:Iodides / Q000737:chemistry; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D008297:Male; D010472:Perchlorates / Q000494:pharmacology; D011877:Radionuclide Imaging / Q000295:instrumentation / Q000379:methods*; D011994:Recombinant Proteins / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D013972:Thyrotropin / Q000378:metabolism*; D013974:Thyroxine / Q000494:pharmacology; D013997:Time Factors
D007454:Iodides; D007457:Iodine Radioisotopes; D010472:Perchlorates; D011994:Recombinant Proteins; D013972:Thyrotropin; D013974:Thyroxine; C494474:perchlorate