Cross references:   Monotreme Dominance Hierarchies  

Monotremes (Wiki) 
    "In common with reptiles and marsupials, monotremes lack the connective structure (corpus callosum) which in placentals is the primary communication route between the right and left brain hemispheres.[2] The anterior commissure does provide an alternate communication route between the two hemispheres, though, and in monotremes and marsupials it carries all the commissural fibers arising from the neocortex, whereas in placental mammals the anterior commissure carries only some of these fibers.[3] "

Introduction to the Monotremata (Goog) 

Order Monotremata (Goog) 

Monotremes (Goog) 

Monotremes and marsupials (Goog) 

NOTE;  Searching Google for "Monotreme endocrinology" yielded only one partially useful hit on the first four pages. 

Platypus (Ornithorhynchus anatinus) Online Resource Guide: BIBLIOGRAPHY (Goog) 
Mcdonald, I. R., Than, K. A., Evans, B. (1988). Glucocorticoids in the blood plasma of the platypus Ornithorynchus anatinus. Journal of Endocrinology 118 (3), 407-16.  
Only abstract available online. 
Not very useful. 

Weiss, M. (1973). Biosynthesis of adrenocortical steroids by monotremes: echidna (Tachyglossus aculeatus) and platypus (Ornithorhynchus anatinus). Journal of Endocrinology 58 (2), 251-62.

NOTE;  Searching Google for "Monotreme endocrine" yielded nothing useful in the first four pages of hits.   

Development of the hypothalamus and pituitary in platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus).