Thyroid gland function and growth in IGF binding protein-1 transgenic mice

Area of Science:

• Endocrinology
• Molecular Biology
• Thyroid Research

Background:

• Insulin-like Growth Factor-I (IGF-I), its receptor, and IGF-binding proteins (IGFBPs) are crucial for thyroid gland function and growth.
• IGFBP-1 specifically modulates IGF-I action, influencing cellular processes within the thyroid.

Purpose of the Study:

• To investigate the in vivo and in vitro effects of elevated IGFBP-1 levels on thyroid gland function and growth.
• To elucidate the role of IGFBP-1 in regulating thyroid hormone production and cellular proliferation.

Main Methods:

• Utilized transgenic mice with constitutive overexpression of IGFBP-1, exhibiting partial inhibition of IGF-I action.
• Assessed thyroid growth, morphology, and hormonogenesis in response to goitrogens (sodium perchlorate, methimazole).
• Evaluated in vitro thyroid follicle proliferation stimulated by IGF-I and Thyroid Stimulating Hormone (TSH).

Main Results:

• Transgenic mice showed increased relative thyroid weight but reduced serum thyroid hormones (T3, thyroxine) and T3-binding capacity.
• Goitrogen-induced thyroid growth was attenuated in transgenic mice, despite higher TSH levels, indicating altered responsiveness.
• In vitro, thyroid follicle proliferation response to IGF-I was diminished in transgenic mice, while TSH response remained unaffected.

Conclusions:

• Overexpression of IGFBP-1 attenuates IGF-I action in vitro but paradoxically enhances thyroid growth in vivo.
• These findings suggest IGFBP-1 influences thyroid function at multiple levels, leading to complex growth and functional outcomes.
• IGFBP-1 plays a significant role in modulating thyroid gland homeostasis and response to stimuli.