What is threptin biscuits made of?

There is no known biscuit called "threptin biscuits". It's possible that you've misheard or misspelled the name.

Could you please double-check the name or provide more context?

Perhaps you are thinking of:

* "Threptin" - This could refer to a brand name or a type of nutritional supplement.

* A different type of biscuit - Do you have any other details about the biscuits, such as their appearance, flavor, or origin?

Please provide more information so I can assist you better!