Endocrine system

The endocrine system is a control system of glands that secrete hormones that circulate within the body via the circulatory system to affect cells within certain organs of the body. The study of the endocrine system was known as endocrinology.

Pa'nar Syndrome affected the endocrine and immune systems as well as causing degradation of the synaptic pathways. 

One of Doctor Phlox's reasons for staying aboard Enterprise was that he was fascinated with the Human endocrine system, according to Captain Jonathan Archer. 

Doctor Christine Chapel pointed out the android Ilia's internal functions were patterned almost identically to the exocrine (and, therefore, endocrine) systems of her parent, Carbon-based lifeform. 

In 2371, Doctor Julian Bashir reported that Zek's endocrine system was in "terrific shape", after Quark had him perform a medical examination on the Grand Nagus.