The hormones that do not cross the placenta are?

Correct option is B

Sol. Insulin and thyroxine do not cross the placenta because of their molecular structure and size. Insulin is a peptide hormone, and thyroxine is regulated tightly by binding proteins, so both are prevented from transferring into fetal circulation, protecting the fetus from excess exposure.
Explanation of each option:
· (a) Thyroxine and Steroids – Steroid hormones can cross the placenta because they are lipid-soluble.
· (b) Insulin and Thyroxine – Correct. Both are restricted from crossing due to molecular size and transport limitations.
· (c) Insulin and Steroids – Steroids can easily pass through the placenta, so this is incorrect.
· (d) Parathormone and Calcitonin – These hormones do not directly relate to placental transfer mechanisms for this question's context.