Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): During pregnancy, the levels of hormones like cortisol, prolactin and thyroxine are increased several folds in the maternal blood.
Reason (R): During pregnancy, the placenta acts as an endocrine tissue and produces hormones like hCG, hPL, estrogens and progestogens.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Both (A) and (R) are true but (R) is not the correct explanation of (A).
During pregnancy the mother’s body works with a new organ, the placenta. It supplies the embryo with oxygen and food, and it also acts as an endocrine tissue. At the same time, the mother’s own glands raise the output of several hormones.
Assertion (A): During pregnancy, the levels of hormones like cortisol, prolactin and thyroxine are increased several folds in the maternal blood. — True. These hormones rise in the mother’s blood along with estrogens and progestogens. The rise supports fetal growth, the metabolic changes in the mother and the maintenance of pregnancy.
Reason (R): During pregnancy, the placenta acts as an endocrine tissue and produces hormones like hCG, hPL, estrogens and progestogens. — True. hCG is human chorionic gonadotropin and hPL is human placental lactogen. The placenta makes these two, along with estrogens and progestogens.
Why R does not explain A? A is about the rise of cortisol, prolactin and thyroxine in the mother’s blood. R is about the hormones that the placenta makes. Cortisol comes from the adrenal cortex, prolactin from the anterior pituitary and thyroxine from the thyroid gland. R does not name any of these three, so it does not account for their rise. Both statements are true, but R is not the reason for A.
NCERT Extract:
Pregnancy and Embryonic Development – “… Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, etc. In the later phase of pregnancy, a hormone called relaxin is also secreted by the ovary. Let us remember that hCG, hPL and relaxin are produced in women only during pregnancy. In addition, during pregnancy the levels of other hormones like estrogens, progestogens, cortisol, prolactin, thyroxine, etc., are increased several-folds in the maternal blood. Increased production of these hormones is essential for supporting the fetal growth, metabolic changes in the mother and maintenance of pregnancy.”