Hello doctor one of my friend has not got her...

How to treat missed period ?
after exclusion of pregnancy as it's the most common cause od missed period , you'll have to do some investigation to detect the cause that could be a result of PCO : in this case you'll be prescribed to take OCP such as cycloprogynova , in cases that suggest hypothyroidism then thyroxin is a good choice , you also have to stay healthy by eating healthy food as well as losing overweight and doing daily sport 
What investigations should be done ?
BHCG Pregnancy test , then thyroid fuction tests TSH , T3 , T4 are requried to diagnose hypothyroidism as well as LH , FSH hormones with Ultrasound to detect PCO 
What are the suspected causes ?
Pregnancy 
Lactating 
PCO 
Hypothyroidism 
Prolactinemia 
Advice :
continue with specialist doctor