Endocrine Changes in Pregnancy

Pregnancy changes endocrine physiology in a predictable sequence. Early in gestation, human chorionic gonadotropin (hCG) briefly stimulates the thyroid. As the placenta grows, estrogen changes thyroid-hormone transport, human placental lactogen shifts maternal metabolism toward insulin resistance, and placental corticotropin-releasing hormone contributes to a physiologic rise in cortisol. The placenta is functioning as an endocrine organ, not merely supporting the fetus. That model helps the nurse interpret an apparently abnormal result. A mildly suppressed first-trimester TSH may reflect hCG rather than hyperthyroidism; a higher total T4 may reflect increased binding protein rather than excess free hormone. Conversely, vomiting with ketones, polyuria with hypernatremia, severe tachycardia with fever, or hypotension that does not respond as expected signals that normal adaptation may have become endocrine disease. The clinical question is not simply whether a value is high or low, but whether the finding fits the gestational pattern and the patient's condition.