PSA vs protein

PSA and protein both are nouns.

Word	Noun	Adjective	Verb	Adverb
PSA	Yes	No	No	No
protein	Yes	No	No	No

As nouns, protein is a hypernym of PSA; that is, protein is a word with a broader meaning than PSA:

PSA: a protein manufactured exclusively by the prostate gland; PSA is produced for the ejaculate where it liquifies the semen and allows sperm cells to swim freely; elevated levels of PSA in blood serum are associated with benign prostatic hyperplasia and prostate cancer
protein: any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes

PSA (noun)	protein (noun)
a protein manufactured exclusively by the prostate gland; PSA is produced for the ejaculate where it liquifies the semen and allows sperm cells to swim freely; elevated levels of PSA in blood serum are associated with benign prostatic hyperplasia and prostate cancer	any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes