Hormones at puberty

A boy reaches puberty when the hypothalamus directs the pituitary gland to increase the secretion of the trophic hormones--luteinizing hormone, follicle-stimulating hormone and adrenocorticotrophic hormones. These act on the testes to start the production of sperm and on the adrenal cortex and testes to produce male hormones, or androgens. Testosterone, the most important androgen, promotes and controls the devlopment of the sex organs and such secondary sexual characteristics as pubic and facial hair. In a girl, the trophic hormones stimulate the ovaries and adrenal glands to secrete androgens that control the shape of the female body. The ovarian hormones, progesterone and estrogen, initiate menstruation.

Anatomy of the Hypothalamus

Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland (hypophysis). The hypothalamus,  is located below the thalamus, just above the brain stem. In the terminology of neuroanatomy, it forms the ventral part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is roughly the size of an almond.

The hypothalamus is responsible for certain metabolic processes and other activities of the Autonomic Nervous System. It synthesizes and secretes neurohormones, often called hypothalamic-releasing hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones. The hypothalamus controls body temperature, hunger, thirst, fatigue, and circadian cycles.