As you can see in the hypothalamus pictures, it measures about the size of an almond or pearl. It is an extremely important part of brain in human beings and other higher animals. Hypothalamus constitutes one of the four major components of diencephalon, while the other three are: thalamus, epithalamus and subthalamus. It is intimately associated with the function of autonomic & endocrine systems, formation of behavioral patterns, temperature control, reproduction, and so on.
With the help of hypophysis
The hypothalamic region in the posterior part of forebrain (diencephalon) initiates, facilitates and accomplishes a number of vital functions in the human body including hunger, circadian cycles, fatigue, sleep, thirst, attachment behaviors and parenting. The neurohormones (chemical substances of the nervous system) secreted by the organ are transferred to the pituitary gland that either inhibit or stimulate its secretary activities. Some of the vital functions of hypothalamus can be summarized.

Malnutrition, inflammation, neoplasm, infection or any other condition of this structure not only adversely affects its functions but also causes severe symptoms in the victim. Such signs need to be addressed as soon as possible. Originating from the adjacent structures, like optic chiasm, hypophysis or optic nerves, the benign or malignant tumors spread to affect the organ and lead to hypothalamic neoplasms. The clinical manifestations of the disorder include loss of vision, precocious puberty, macrocephaly and developmental delay. The frequently recommended treatment measures of the tumors include radiations and surgical therapy.
Hypopituitarianism is another ailment of brain in which pituitary gland and hypothalamus are integrated with each other, thus inhibiting the hormonal secretions of hypophysis and disturbing all the vital functions of the body that are regulated by the chemical substances produced therein. In this case, your health care provider may suggest hormonal replacement therapy as the disease results in the hormonal insufficiency in the body.