mechanism

Last reviewed 12/2022

DUB may be due to an alteration in the output, or balance, of gonadotrophic or ovarian hormones, and/or an endometrial defect in the secretion or release of prostaglandins. In most cases, cycles are anovulatory.

Immediately after puberty and near to the menopause, DUB is frequently attributed to an inadequate ovarian response to FSH. The endometrium is inadequately stimulated on account of the reduced production of oestrogen, producing irregular bleeding.

In other cases, oestrogen production is prolonged resulting in cystic hyperplasia of the endometrium, a syndrome known as "metropathia haemorrhagica." The basis is absence of feedback inhibition of pituitary FSH secretion. Amenorrhoea occurs initially but after 6-8 weeks, is followed by excessive endometrial shedding as oestrogen levels fall.

DUB may also occur because of increased production of prostacyclin - PGI2 - and / or PGE2, with a relative decrease in PGF2-alpha. These prostaglandins are synthesised by the endometrium and myometrium from arachidonic acid. Their effects are:

• PGI2 - myometrial relaxation and vasodilation; platelet inhibition
• PGE2 - mymoetrial contraction and vasodilation
• PGF2-alpha - myometrial contraction and vasoconstriction