Page 68 - The Cell in 40 Topics

s everyone is well aware, during adolescence—the transi-
tional stage between childhood and adulthood—the
body undergoes a large number of changes, many simul-
taneously. But what mechanism so accurately regulates the timing of and
initiates these changes inside the bodies of billions of people? It is as if there
were an alarm clock in the human body, and when the clock rings, certain
hormones are awakened and go into action.
There is no clock in the body, of course. But as we shall be seeing
shortly in some detail, certain cells in the hypothalamus region of the brain
go into action after a delay of some 12 to 13 years, just as if they had heard
an alarm clock going off. At a specific age, cells in the hypothalamus begin
secreting a hormone known as GnRH. This hormone issues a command to
the pituitary gland to begin producing two hormones known as the follicle
stimulating hormone (FSH) and luteinizing hormone (LH).
These two hormones have very important duties and miraculous abil-
ities. Both initiate the process of diversification and maturation in both the
male and female bodies—.a very important detail, because FSH and LH

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