Final answer:
Puberty is regulated by the hypothalamus through the secretion of GnRH, which stimulates the anterior pituitary to release FSH and LH, inducing gonadal secretion of sex steroid hormones. Sensitivity to negative feedback decreases during puberty, allowing hormone levels to rise and triggering secondary sexual characteristics. Abnormal hypothalamic function can disrupt this process and affect sexual maturity.
Step-by-step explanation:
Hormonal Control of Puberty and Hypothalamic Syndromes
The onset of puberty is primarily controlled by the hypothalamus, which secretes gonadotropin-releasing hormone (GnRH). GnRH stimulates the anterior pituitary gland to release gonadotropins, which include Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH). These gonadotropins in turn regulate the gonads – ovaries in females and testes in males. The release of sex steroid hormones, such as testosterone and estrogen, is critical for the development of secondary sexual characteristics.
During the approach of puberty, there are changes in the sensitivity of the negative feedback system involving the hypothalamus and pituitary. Initially, the system is highly sensitive, and low levels of sex hormones are enough to inhibit the production of GnRH. As puberty progresses, this sensitivity diminishes, which allows for increased levels of sex hormones. Pituitary tumors can affect this timing, leading to early or late onset of puberty. Abnormalities in the hypothalamus, such as those observed in Prader-Willi Syndrome (PWS), can prevent individuals from reaching sexual maturity.
The increase in the production of gonadotropins and the corresponding rise in sex hormones are required for puberty-associated changes such as growth spurts, the maturation of reproductive organs, and the appearance of secondary sexual characteristics. The first detectable change, often starting around the age of eight or nine, is the nocturnal release of LH, which continues to increase throughout adolescence.