Complex sentence: Neuroendocrinology arose from the recognition that the brain, especially the hypothalamus, controls secretion of pituitary gland hormones, and has subsequently expanded substantially to study numerous interconnections of the endocrine and nervous systems.
Split into simpler sentences: Neuroendocrinology arose from the recognition that the brain, especially the hypothalamus, controls secretion of pituitary gland hormones. Neuroendocrinology has subsequently expanded substantially to study numerous interconnections of the endocrine and nervous systems.