A. Glucagon is secreted from alpha cells of islets of Langerhans of pancreas. It increases blood sugar level by stimulating glycogenolysis (i.e. break down of glucose) and gluconeogenesis (synthesis of glucose).
B. Thyroxine is secreted from thyroid gland. It stimulates the consumption of oxygen by metabolically active tissues and also increases the oxidation of glucose in tissues.
C. Parathormone is secreted from parathyroid gland and increases calcium reabsorption from the bones and causes mobilization of calcium in the blood.
D. Calcitonin is secreted from the C -cells of thyroid gland and acts on bone and kidneys to reduce blood calcium level.
Hence, blood calcium level is increased by parathormone.
So, the correct answer is 'Parathormone'.