Pitressin vs pressor

Pitressin and pressor both are nouns.

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

As nouns, pressor is a hypernym of Pitressin; that is, pressor is a word with a broader meaning than Pitressin:

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: 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

Other hypernyms of Pitressin include vasoconstrictive, vasoconstrictor, endocrine, hormone, internal secretion.

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