To      : Diane Wiessinger
Re      : Calcitonin

Calcitonin is a large polypeptide hormone(32 amino acids) secreted by the
parafollicular cells of the thyroid.  Calcitonin regulates calcium and bone
metabolism in mammals.

Calcitonin derived from salmon has been found to inhibit lactation in animals.
 We do not know if it does so in humans.  It is not known if it is secreted
into human milk,  but due to its size,  I sort of doubt much would be.

In addition,  its oral bioavailability is negligible because it is destroyed by
the gastric acid and proteases prior to absorption.

Tom Hale