Prepubertal OVX increases IGF-I expression and bone accretion in C57BL/6J mice

Area of Science:

• Endocrinology
• Skeletal Biology
• Reproductive Biology

Background:

• Estrogen is widely believed to drive pubertal bone growth via growth hormone (GH)/insulin-like growth factor (IGF) signaling.
• The precise role of estrogen in mediating pubertal skeletal changes requires further investigation.

Purpose of the Study:

• To investigate the causal relationship between estrogen and the GH/IGF axis in pubertal bone development.
• To determine the effects of estrogen loss on skeletal parameters and IGF-I production in prepubertal mice.

Main Methods:

• Ovariectomy (OVX) was performed on prepubertal mice (3 weeks old).
• Skeletal changes, body composition, and IGF-I levels were assessed post-OVX.
• A second experiment involved estrogen replacement therapy in OVX mice.

Main Results:

• OVX led to increased body weight, bone mineral content, bone length, bone size, and serum/tissue IGF-I levels.
• OVX also resulted in decreased total body fat.
• Estrogen treatment partially reversed weight and bone size increases, and fully restored body fat and IGF-I levels.

Conclusions:

• Contrary to expectations, loss of estrogen in prepubertal mice enhanced IGF-I production and bone accretion.
• These findings challenge the established view of estrogen solely as an initiator of the pubertal growth spurt.
• Estrogen's role in pubertal bone development is more complex than previously understood, involving regulation of IGF-I and bone formation.