Thyroid-Stimulating Hormone (TSH). Guide. A thyroid-stimulating hormone (TSH) blood test is used to check for thyroid gland problems. TSH is produced when the hypothalamus releases a substance called thyrotropin-releasing hormone (TRH). TRH then triggers the pituitary gland to release TSH.
A Raven is black but depending on which way the light hits it they change to other colors like bluish, dark red, or greenish. There are white Ravens but are not albino.
I have always thought it was because a raven is not like a writing desk and a writing desk is not like a raven and since they have something in common then a raven is like a writing desk. But that's just my answer.