Rl. Jones et Hod. Critchley, Morphological and functional changes in human endometrium following intrauterine levonorgestrel delivery, HUM REPR, 15, 2000, pp. 162-172
The levonorgestrel releasing intrauterine system (LNG-IUS) provides a novel
contraceptive method. Intrauterine LNG induces a dramatic transformation o
f the endometrium, characterized by extensive decidualization, This is asso
ciated with strong expression of local factors associated with decidualizat
ion, including prolactin receptor and insulin-like growth factor binding pr
otein-1. A striking discovery was the down-regulation of oestrogen and prog
esterone receptors in all components of the endometrium after insertion of
the LNG-IUS, with a gradual return between 6 and 12 months post-insertion.
Preliminary findings suggest that androgen receptors are expressed during t
his time. Elevated leukocyte infiltrate is observed 1 month after insertion
of the device, comprising large granular lymphocytes and macrophages, We e
xamined a number of local mediators implicated in menstruation and breakthr
ough bleeding episodes. Expression of the chemokine interleukin-g was enhan
ced after insertion of the device, with a notable decrease apparent 6 month
s post-insertion. Cyclooxygenase-2 was similarly strongly expressed in the
first months after LNG-IUS insertion, in contrast to an initial suppression
of prostaglandin dehydrogenase activity. By deduction it appears that high
er local concentrations of prostaglandins are present in the initial period
of local LNG exposure. Taken together these data suggest that in the first
months following LNG-IUS insertion steroid receptor content is significant
ly decreased, resulting in the altered expression of many locally acting me
diators which may be involved in breakthrough bleeding episodes.