The hypthalamus is defined as a portion of the brain that contains a number of small nuclei. These nuclei have a variety of different functions. One of the most important functions within this is the inking of the nervous system to the endocrine system.
The hypthalamus indirectly controls growth from infancy to adulthood by keeping active and telling the growth hormone to regulate.
According to Wikipedia, one of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland. When the thyroid receives thyroid stimulating hormone (TSH) from the pituitary gland it produces triiodothyronine which is commonly referred to as T3, thyroxine which is commonly known as T4, and calcitonin.