The thickened endometrium
means thickened uterine lining. It is this layer which is shed off in menses.
Since your wife has irregular periods
, its natural that this layer would get thicker as its not being shed off monthly in your wife's case.
Rest of your ultrasound is normal. You have not mentioned about the ovaries. If they show cysts, it means your wife has a condition called Polycystic ovarian syndrome
where in there is irregular periods, weight gain, pimples, hairy body and face along with infertility.
The best way to regularize periods is by using Oral contraceptive pills
(birth control pills) if you do not desire pregnancy.
OCPS will not treat the cause. Depending on the cause of irregular periods you have to take definite treatment along with ocps.
For example, if your wife has PCOS then she needs to take metformin along with OCPS. Treatment is different in case she wants to conceive.
If she has a thyroid disorder
which also cause irregular periods then you need to take thyroid supplements .