Somatostatin is secreted by

Somatostatin is secreted from the hypothalamus. It inhibits the release of growth hormone from the pituitary. 

The hypothalamus is the basal part of diencephalon, forebrain and it regulates a wide spectrum of body functions. It contains several groups of neurosecretory cells called nuclei which produce hormones. These hormones regulate the synthesis and secretion of pituitary hormones.