- Differential modulation of transforming growth factor-beta by betamethasone-17- valerate and isotretinoin: corticosteroid decreases and isotretinoin increases the level of transforming growth factor-beta in suction blister fluid. Leivo, T., Arjomaa, P., Oivula, J., Vesterinen, M., Kiistala, U., Autio, P., Oikarinen, A. Skin Pharmacol. Appl. Skin Physiol. (2000)