The endocrine glands i n Xenentodon are hypophysis, pineal, thyroid, thymus, corpuscles of Stannius, interrenal, post-branchial, urophysis and the islets of Langerhans.
The pituitary has the usual structure, however, the pars intermedia is centrally situated. Such a condition has so far been reported in only a few teleosts. The pineal is an elongated structure with a definite stalk. Numerous pigment granules are found in the pineal cells. Thyroid follicles surround the ventral aorta in the pharyngeal region. Thymus is present inside the pharynx dorsal to the branchial region on each side. It is without a peduncle and has simple structure. There are two corpuscles of Stannius one on each side of the median line. The internal cavity in each is filled with lamellae of simple epithelial tissue. The outer capsular wall is made up of flattened cells and is not fibrous. The anterior portion of each kidney has become modified into the interrenal body. Although renal in origin the interrenal bodies appear to function as the endocrine organs in the adult. Post-branchial body lies squeezed between the oesophagus and the sinus venosus. Larger cells show lobulated nuclei. Urophysis forms a ventral enlargement at the caudal end of the spinal cord. There is great concentration of Dahlgren cells in the region of the Urophysis proper. The processes from these cells p ass into the urophysis. Extensions of the pia mater into the urophysis are absent in this fish. There is a single islet of Langerhans. This endocrine portion of pancreas stains lighter than the exocrine portion.