Homeostatic mechanisms controlling growth hormone involve negative feedback by GH and what other hormone?

Growth-hormone-inhibiting hormone or somastostatin.

Explanation:

Basically the GH is secreted by the anterior pituitary glands under the regulations of certain secretory nuclei in the hypothalamus. The cells of these nuclei secrets two hormones,

1. growth hormones releasing hormone which stimulate growth hormones releasing-receptors receptors for the pituitary glands to secrets growth hormones,

and

2. the Growth-hormones-inhibiting hormones. This hormone is secreted, and carried in the blood stream by hypothalamo-hypophsial-portal circulation in response to elevated levels of GH. They inhibit the secretion of Growth hormones in the pituitary glands; by inhibiting the activities of growth-hormones - releasing hormone, preventing them from binding with growth-hormone-releasing hormones receptors in the anterior pituitary gland, therefore inhibiting GH secretions.