The level of which hormone is unchanged in pregnancy
**Core Concept**
Pregnancy is a complex physiological state characterized by various hormonal changes. The levels of several hormones increase or decrease during pregnancy to support fetal development and maternal health. However, some hormones remain unchanged to maintain homeostasis.
**Why the Correct Answer is Right**
The hormone that remains unchanged in pregnancy is adrenocorticotropic hormone (ACTH). This is because the negative feedback mechanism involving cortisol and corticosteroid-binding globulin (CBG) maintains a stable level of ACTH. The increase in cortisol-binding globulin (CBG) during pregnancy binds more cortisol, preventing a decrease in ACTH. Additionally, the placental production of cortisol and corticosteroids does not significantly affect the ACTH levels.
**Why Each Wrong Option is Incorrect**
**Option A:** Aldosterone levels increase in pregnancy due to the increased production of progesterone, which stimulates the renin-angiotensin-aldosterone system (RAAS). This leads to an increase in blood volume and cardiac output.
**Option B:** Estrogen levels increase significantly in pregnancy, reaching 100- to 200-fold higher than pre-pregnancy levels. This increase is essential for maintaining pregnancy and fetal development.
**Option C:** Progesterone levels also increase in pregnancy, supporting implantation and maintenance of pregnancy. The increase in progesterone is crucial for fetal development and preparing the uterus for childbirth.
**Option D:** Human chorionic gonadotropin (hCG) levels increase in pregnancy and remain elevated until the placenta takes over hormone production. hCG is essential for maintaining pregnancy and supporting embryonic development.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that changes in hormone levels during pregnancy can affect various physiological processes, including blood pressure, glucose metabolism, and immune function. Recognizing these changes is crucial for providing appropriate prenatal care and managing potential complications.
**Correct Answer:** D. Human chorionic gonadotropin (hCG) levels are unchanged in pregnancy