The insulin-like growth factor-I system and hormone replacement therapy

Area of Science:

• Endocrinology
• Reproductive Medicine
• Molecular Biology

Background:

• Hormone replacement therapy (HRT) is used for menopausal symptoms.
• Insulin-like growth factors (IGFs) play roles in cell growth and metabolism.
• The impact of different HRT formulations on IGFs is not fully understood.

Purpose of the Study:

• To investigate the effects of various HRT regimens on plasma concentrations of free and total IGF-I, IGF binding protein (BP)-1, and IGFBP-3.
• To compare the influence of oral versus transdermal administration routes of estrogens and progestins on IGF parameters.

Main Methods:

• A clinical study involving seventy-one postmenopausal women.
• Four HRT regimens were administered over six cycles: oral conjugated estrogens, transdermal estradiol, oral conjugated estrogens with norethisterone, and transdermal estradiol with norethisterone acetate.
• Plasma levels of free/total IGF-I, IGFBP-1, and IGFBP-3 were measured pre- and post-treatment.

Main Results:

• Oral conjugated estrogens decreased total IGF-I and increased free IGF-I and IGFBP-1.
• Transdermal estrogens did not alter total or free IGF-I or IGFBP-1.
• Combined oral or transdermal therapies with progestins generally increased free IGF-I and IGFBP-1, with variable effects on total IGF-I.
• IGFBP-3 levels remained unchanged across all groups.

Conclusions:

• The route of HRT administration significantly influences total and free IGF-I concentrations.
• Transdermal estrogen therapy appears to have a neutral effect on IGF-I and IGFBP-1 levels.
• Elevated free IGF-I was observed in most HRT groups, except for transdermal estrogen use.