Usually regular period but am 16 d late. Not preg normal tsh but low iron (6.42) &prolactin level 42.84 ng/ml. Can it be the cause of missed period?

It can be the cause. Hyperprolactinemia can cause you to miss your period. Further work up and a radiographic evaluation of your pituitary gland by MRI or CT scan are recommended.
Hormonal imbalance. If you did not have sex since your last period, you are not pregnant. Menstrual irregularities are not uncommon and anovulatory cycle is a common cause. If you miss more than two periods it would be time to see your doctor. If you do not wish to be pregnant, use contraception all the time. You may consider implanted contraceptive or an IUD. Consult this site for more information on this topic. http://www.nichd.nih.gov/health/topics/menstruation/conditioninfo/Pages/causes.aspx Practice safe sex, if you have sex.