Quantitative analysis of thyroid-stimulating hormone messenger RNA and heterogeneous nuclear RNA in hypothyroid rats

Thyroid-stimulating hormone (TSH) stimulates the synthesis and release of thyroid hormones including triiodothyronine (T3) and thyroxine (T4). Semiquantitative analyses using northern blot and in situ hybridization suggested that TSH gene transcription is upregulated under conditions of hypothyroidism. However, no quantitative analysis of TSH gene expression using real-time polymerase chain reaction (PCR) has been reported. In this study, we quantitated the TSHβ messenger ribonucleic acid (mRNA) level as well as the TSHβ heterogeneous nuclear ribonucleic acid (hnRNA) level in the anterior pituitary of hypothyroid rats, by real-time PCR using the LightCycler^® system. The hnRNA is the primary deoxyribonucleic acid (DNA) transcript, which reflects the transcription rate more reliably than the mRNA because of its short half-life. In the anterior pituitary of rats with methimazol-induced chronic hypothyroidism, both mRNA and hnRNA expression of TSHβ were upregulated fourfold relative to normal rats (n = 4). Our method provides a rapid and accurate measure of gene transcription. In the present report, we described a technique for accurate measurement of TSHβ hnRNA level.