Besides the MMP system, Knappe et al. also investigated the expression of the serine proteases urokinase-type plasminogen activator (uPA), the tissue-type plasminogen activator (tPA), the uPA receptor (uPAR), and the plasminogen activator inhibitor-1 (PAI-1) in a large series of 84 pituitary adenomas (18 cases of acromegaly, 21 Cushing’s diseases, 18 prolactinomas, 1 TSH-secreting adenoma, and 26 non-secreting adenomas) and 9 normal pituitaries. Here, PLAT is linked to acromegaly.