In the second trimester, what happens with the fetal endocrine system?

• A. It starts producing the most hormones
• B. It stops producing hormones
• C. It remains inactive
• D. It depends on maternal hormones

Answer: (A)

During the second trimester, the fetus’ endocrine system becomes more active as its glands mature and begin secreting hormones that coordinate growth and organ development. The fetal pituitary, adrenal glands, thyroid, and pancreas start functioning more prominently, producing hormones like cortisol for lung and tissue maturation, thyroid hormones for brain development and metabolism, and insulin for glucose use. Meanwhile, the placenta still provides hormonal support to maintain the pregnancy, but the fetus is increasingly producing its own hormones rather than relying solely on maternal signals. This shift toward autonomously producing hormones explains why the fetal endocrine system is described as starting to produce more hormones during this period.