What Causes Delayed Periods Along With Thyroid Problem?

Hi ,
My fiance is having certain problems in her periods.
She took cabgolin tablets for six months
all her sonography and prolactic level was normal
she went to the doctor becoz her prolactin level was high it was 86
which was meant to be under 50.
Doctor prescribed her the cabgolin tablets
she had normal period on the right date in feb
but in march the date have passed out and its been 6 days now
she have a lil percent of thyroid ,.
Thanks