Good day, i am a 27 year old female with an under active thyroid. that being said, i am severely underweight. i eat healthy and often but can't seem to put on any weight. what can i do?

This is a head: scratcher! As you know, typically we expect those with an underactive thyroid gland to gain weight. Severe underweight needs a comprehensive medical evaluation to exclude genetic causes, metabolism issues, drug use, eating disorder and or combination of physical and mental problems.Find a metabolic specialist/possibly Endocrinologist and work to find diagnosis and effective treatment. Good wishes