Human reproduction
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The mechanisms responsible for progestogen-induced breakthrough bleeding remain unexplained. The aim of the present study was to examine the expression of three basement membrane components, collagen IV (CIV), laminin and heparan sulphate proteoglycan (HSPG), by immunohistochemistry in sections of endometrium from women receiving the subdermal levonorgestrel implant (Norplant) and normally cycling women. Control biopsies were obtained from 20 normal subjects from Melbourne, Australia, and pre- and post-Norplant-insertion biopsies were obtained from 11 women from Sydney, Australia, with between 3 and 6 months Norplant exposure. ⋯ During the normal cycle, HSPG was only detected in approximately 40% of vessels with CIV and laminin immunoreactivity, and menstrual biopsies demonstrated reduced staining for all three components. Several biopsies exhibited a degree of regional variability in staining intensity, and Norplant biopsies exhibited areas of discrete, decidual-like stromal immunostaining for CIV and laminin. Although no differences were found in microvascular basement membranes in Norplant users that might explain capillary fragility, it is possible that other techniques could yield information on changes in the integrity of basement membrane components that might influence basement membrane strength.