The expression and cellular distribution of transforming growth factor-1 (TGF beta 1) through TGF beta 3 and TGF beta type I-III receptor messenger ribonucleic acid (mRNA) and protein were analyzed in leiomyomata from patients receiving GnRH agonist (GnRHa; leuprolide acetate) compared to those in untreated controls. Standard reverse transcription-PCR revealed that the unaffected myometrium and leiomyomata from leuprolide-treated and untreated patients express TGF beta 1-3 and TGF beta type I-III receptor mRNA. The myometrial and leiomyomata smooth muscle cells were the primary site of TGF beta 1-3 and TGF beta type I and II receptor mRNA and protein expression, as determined by in situ hybridization and immunohistochemical localization. These observations indicate that leiomyomata express a higher of level of TGF beta and TGF beta receptor mRNA and protein than unaffected myometrium during the secretory phase of the menstrual cycle, and women who received leuprolide acetate therapy had a substantially lower level of expression than untreated controls. Furthermore, competition-based quantitative reverse transcription-PCR using synthetic internal standards revealed that leiomyomata express a significantly higher number (copies per cell) of TGF beta type II receptor mRNA, followed by TGF beta 1, TGF beta type I receptor, TGF beta 2, and TGF beta 3 (P < 0.05). However, there was a significant decrease in the levels (copies per cell) of TGF beta 1, TGF beta 3, and TGF beta type I and type II receptor mRNA expression in leiomyomata from leuprolide-treated compared to untreated patients (P < 0.05). The data provide further evidence that leiomyomata express mRNA and protein for all components of the TGF beta system, and GnRHa therapy results in down-regulation of their expression. More specifically, these data suggest that TGF beta 1 and TGF beta 3 may play a more important role in leiomyomata growth than TGF beta 2, which leads us to propose that lowering TGF beta and receptor expression may have a direct effect on leiomyomata regression.