Puberty and the HPG Axis

Study Notes

Puberty and HPG Axis

Puberty begins with the activation of the hypothalamic-pituitary-gonadal (HPG) axis.
The anterior hypothalamus synthesizes and releases gonadotropin-releasing hormone (GnRH), which stimulates the anterior pituitary to release gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH).
LH and FSH stimulate gonadal steroid release and gamete production.

HPG Axis Activation Periods

The HPG axis has three activation periods: during fetal life, a "mini-puberty" from the first week of life to 6 to 9 months of age, and finally, after childhood, which is the period commonly defined as puberty.

Development of GnRH-Secreting Neurons

GnRH-secreting neurons originate from the epithelium of the medial olfactory pit at about 40 days' gestation.
These neurons migrate along nerve fibers to the hypothalamus.

HPG Axis Activation During Fetal Life

HPG axis activation during fetal life allows for reproductive organ development.
It is also thought to be responsible for central programming, which leads to sex dimorphic body composition later in life.

Suppression of HPG Axis

Placental estrogens increase at 37 to 40 weeks' gestation and suppress the HPG axis in early infancy.
After birth, gonadotropin levels initially decline, and then increase again at 6 to 10 days after birth.

Description

This quiz covers the process of puberty, including the activation of the hypothalamic-pituitary-gonadal axis, and the role of various hormones in gamete production and gonadal steroid release. Learn about the three activation periods of the HPG axis and how it affects human development.