From reno- +‎ -in.

• (UK) IPA^(key): /ˈɹiː.nɪn/

• Audio (Southern England):

  (file)

• (US) IPA^(key): /ˈɹi.nɪn/, /ˈɹɛ.nɪn/

renin (countable and uncountable, plural renins)

1. (biochemistry) A circulating enzyme released by mammalian kidneys that converts angiotensinogen to angiotensin I. Due to its activity which ultimately leads to the formation of angiotensin II and aldosterone, this hormone plays a role in maintaining blood pressure.

• angiotensinogenase

• rennin

• inner, niner