Question

Which of the following hormones is a steroid?
(a) Oestrogen
(b) Insulin
(c) Glucagon
(d) Thyroxine

Answer 1

Steroids are the organic compound derived from cholesterol. They are a part of endocrine system hormones. Steroid hormones are of two types: Corticosteroids (synthesised in adrenal cortex) and sex steroids (synthesised by gonads or placenta).

Complete answer:
-Oestrogen is a sex steroid hormone, which is though produced by both men and women. But is considered very important in females due to its role during puberty and menstruation. Thus, Oestrogen, in general, is known as the female sex hormone.
-All steroids have four interlocking rings and are attached either on one or two sides with the other ring. They only differ in a single atom or chemical bond from the other steroids.
-Steroid hormones are basically lipid hormones that are usually ketones or alcohols and so their names usually end with ‘-ol’ or ‘-one’. For example, estradiol (a female oestrogen), testosterone (a male androgen), progesterone, aldosterone, and cortisol.
Figure 1(a): General structure of Oestrogen

Additional Information:
-Steroid hormones being cholesterol-rich lipids are insoluble in water, which helps them to easily diffuse through the cell plasma membrane and also they are carried in the blood by transport protein. This association with transport protein helps steroid hormones to circulate in the blood for a longer time.
-Oestrogen is needed by females for puberty, menstrual cycle, maintaining cholesterol levels, for bone strength, and during pregnancy.
-Oestrogen in males is secreted in low amounts by adrenal gland and testis. Their role is not well studied and is just known to affect sperm count.
-Cholesterol in humans have three fates in steroid hormone production, they can either become cortisol glucocorticoid or the sex steroid hormones like progesterone or androsterone. Progesterone inturn can interconvert into either glucocorticoid on the addition of a water molecule and can form an androsterone on losing an ethyl group (Figure 2).

Figure 2: Structures of other steroid hormones

Note:
Oestrogen, insulin, thyroxine and glucagon are all associated with the endocrine system. Oestrogen is a steroid sex hormone secreted by gonads, thyroxine is an amino acid derived non-steroid hormone secreted by the thyroid gland, Insulin and glucagon are also amino acid-derived non-steroid, fat insoluble hormones secreted by the pancreas.