Is tsh normal in pregnancy?

Not always: Tsh and hcg, the pregnancy hormone, have very similar structures, and some biologic cross-reactivity. The high levels of HCG in pregnancy can provide enough stimulation to the thyroid to cause the thyroid to be just a little overactive and TSH to drop into the slightly low range. This is common and does not usually need treatment. A high tsh, should be treated in almost almost pregnant patients.