All are steroids except -

Ans. is'd' i.e., Thyroxine Steroidso Steroids are complex molecules consisting offour fused carbon rings. There is a phenanthrene nucleus made of three six-membered rings (A,B,C, rings), and a cyclopentane which forms D ring. The fully saturated parent compound (steroid) is known as cyclopentanoperhydrophenaihrene. The alcohol derivatives of steroids, in which one or more OH groups are present in the steroids nucleus, are termed sterols, i.e. sterols are a class of steroids containing hydroxy (OH) group. Cholesterol, ergosterol, coprosterol and sitosterol are some important sterols.o In animal tissues, Cholesterol is the major sterol. Functionally, cholesterol is a very important molecule being precursor of a variety of steroids -Steroid hormones Progesterone, estrogen, androgens (Testosterone), glucocorticoids, mineralocorticoids.Bile acids:- Cholic acid.Chenodeoxycholic acid,Vitamin Do So, all above mentioned compounds have cyclopentanoperhydrophenanthrene nucleus.