Which of the following hormones are secreted directly by the hypothalamus?

Of the hormones listed, only dopamine is secreted directly by the hypothalamus. The hypothalamus synthesizes and releases dopamine into the hypothalamic-pituitary portal system, which then acts on the anterior pituitary gland to regulate the secretion of other hormones such as prolactin.
Calcitonin is secreted by the thyroid gland, not the hypothalamus. Melatonin is secreted by the pineal gland, which is located in the brain but not part of the hypothalamus-pituitary axis. Oxytocin is synthesized in the hypothalamus but is then transported to and released by the posterior pituitary gland.