ADH (vasopressin) is synthesized by hypothalamic neurosecretory neurons, transported axonally (neurocrine mechanism), and secreted from the posterior pituitary directly into the blood circulation to act on distal target organs such as kidneys (endocrine mechanism).

Assertion (A) is correct: Milk fever (parturient paresis) occurs commonly within 48 hours of parturition in high-producing dairy cows. Reason (R) is also factually correct: copious milk secretion creates a huge demand for blood glucose for lactose synthesis (which can cause ketosis). However, Milk Fever is pathophysiologically caused by acute hypocalcemia (sudden loss of blood calcium into colostrum), not glucose drain. Thus, (R) is NOT the correct explanation of (A).

Beta-endorphin is derived from the post-translational processing of the precursor polyprotein Pro-opiomelanocortin (POMC), which is synthesized predominantly by the corticotropic cells in both the anterior lobe and the intermediate lobe of the adenohypophysis (pituitary gland).