Weight gain in seen in all, except -

insulinoma is a condition in which there is excessive insulin production occasionally occurs from an adenoma of an islet of Langerhans. Insulin is an anabolic hormone which causes weight gain. Myxedema develops in the patient with almost total lack of thyroid hormone function . here greatly increased quantities of hyaluronic acid and chondroitin sulfate bound with protein form excessive tissue gel in the interstitial spaces and this causes the total quantity of interstitial fluid to increase .because of the gel nature of excess fluid , it is mainly immobile and the edema is non pitting which results in weight gain . Cushing's disease is characterized by adenomas of anterior pituitary that secrete large amounts of ACTH . here occurs mobilization of fat from the lower pa of the body with concomitant extra deposition of fat in the thoracic and upper abdominal regions . The excess secretion of steroids also leads to an edematous appearance leads to weight gain .Reference -Guyton and Hall Textbook of Medical physiology A South Asian edition, page no . 574,602,603,621