No, renin is an enzyme that catalyzes the conversion of angiotensinogen, a precursor and a protein to angiotensin I.
Thymosin
MSH- Melanocyte stimulating hormone- is secreted by the intermediate lobe of the pituitary gland.
In short, the endocrine system.
Rennin or chymosin is secreted in the fourth stomach of a cow. See the related link for more information.