parathyroid vs endocrine gland

parathyroid and endocrine gland both are nouns.

Word	Noun	Adjective	Verb	Adverb
parathyroid	Yes	No	No	No
endocrine gland	Yes	No	No	No

As nouns, endocrine gland is a hypernym of parathyroid; that is, endocrine gland is a word with a broader meaning than parathyroid:

parathyroid: any one of four endocrine glands situated above or within the thyroid gland
endocrine gland: any of the glands of the endocrine system that secrete hormones directly into the bloodstream

Other hypernyms of parathyroid include ductless gland, endocrine.

parathyroid (noun)	endocrine gland (noun)
any one of four endocrine glands situated above or within the thyroid gland	any of the glands of the endocrine system that secrete hormones directly into the bloodstream