pressor vs Pitressin

pressor and Pitressin both are nouns.

Word	Noun	Adjective	Verb	Adverb
pressor	Yes	Yes	No	No
Pitressin	Yes	No	No	No

As nouns, Pitressin is a hyponym of pressor; that is, Pitressin is a word with a more specific, narrower meaning than pressor:

pressor: any agent that causes a narrowing of an opening of a blood vessel: cold or stress or nicotine or epinephrine or norepinephrine or angiotensin or vasopressin or certain drugs; maintains or increases blood pressure
Pitressin: hormone secreted by the posterior pituitary gland (trade name Pitressin) and also by nerve endings in the hypothalamus; affects blood pressure by stimulating capillary muscles and reduces urine flow by affecting reabsorption of water by kidney tubules

pressor (noun)	Pitressin (noun)
any agent that causes a narrowing of an opening of a blood vessel: cold or stress or nicotine or epinephrine or norepinephrine or angiotensin or vasopressin or certain drugs; maintains or increases blood pressure	hormone secreted by the posterior pituitary gland (trade name Pitressin) and also by nerve endings in the hypothalamus; affects blood pressure by stimulating capillary muscles and reduces urine flow by affecting reabsorption of water by kidney tubules

pressor (adjective)	Pitressin (adjective)
increasing (or tending to increase) blood pressure