Thyroid-Stimulating Hormone (TSH)

Congenital hypothyroidism is a disease associated with loss of function of the thyroid gland. Onset is in infancy, and symptoms can include sleepiness, decreased activity, difficulty feeding, constipation, intellectual disability, and growth retardation. The incidence of congenital hypothyroidism is estimated to be ~ 1 in 2,000.

Gene analysis for the various targeted mutations is performed by polymerase chain reaction and melting curve analysis to detect the mutant and wild-type forms of the gene.  Sequence-specific oligonucleotide probes are labeled with fluorescent dyes, which hybridize to their complementary sequence target in PCR products. The fluorescence resonance energy transfer (FRET) from one fluorophore to another adjacent fluorophore is measurable and is directly proportional to the amount of target DNA generated during PCR. Allele-specific melting curves are generated by slow thermal denaturing of the probe: template hybrid.  Melting curves are generated by monitoring fluorescence throughout denaturation, and melting peaks are generated by plotting the inverse derivative of fluorescence versus temperature (−dF/dT).