Exemestane

Also known as: exemestane, Aromasin (branded), steroidal aromatase inhibitor

Hormone Restoration

In plain English

Exemestane lowers estrogen by permanently switching off the enzyme that makes it. It is FDA-approved for certain breast cancers. In hormone therapy it is sometimes used to reduce estrogen levels. It is taken as a tablet or capsule.

The science

Exemestane is an oral steroidal (irreversible, 'suicide') aromatase inactivator, structurally related to androstenedione, that permanently binds and inactivates aromatase to lower estrogen. It is FDA-approved for hormone-receptor-positive breast cancer; the MAP.3 randomized trial (Goss 2011) showed a 65% relative reduction in invasive breast cancer among higher-risk postmenopausal women, supporting a chemopreventive effect. Because it is steroidal, it has weak androgenic properties and a somewhat different side-effect and lipid profile than non-steroidal AIs. Use in men for estrogen control is off-label with limited dedicated evidence; estrogen deprivation risks (bone loss, arthralgia) apply. Compounded exemestane is not an FDA-approved formulation.

References

• Goss et al., N Engl J Med 2011 (MAP.3 exemestane prevention trial)