Human Endocrine System

The correct option is (A) : I₁₃₁

I-131, sometimes known as iodine-131, is a radioactive element. Cancer of the thyroid is treated with it. The thyroid gland absorbs iodine from the blood in order to synthesise the hormone thyroxine, which is made from iodine. It is concentrated in the thyroid gland when radioactive iodine is administered to a cancer patient in modest doses because the thyroid gland absorbs radioactive iodine from the blood, which kills thyroid gland cells. Therefore, the enlarged thyroid tissue can be destroyed by radioactive iodine.

The correct option is (C) : Estrogen

A neuropeptide secreted by the posterior pituitary is called oxytocin. Milk production mostly utilises prolactin. The anterior pituitary produces GnRH, which promotes the release of LH and FSH. The blood plasma level of oestrogen will be impacted if both ovaries are removed because theca interna cells of Graafian follicles generate oestrogen. The hormone known as oestrogen is primarily responsible for controlling how female accessory reproductive organs, secondary sexual characteristics, and sexual behaviour grow and develop.

This is due to the deficiency of parathormone and is also called parathyroid hormone. It is produced by the parathyroid glands that are located in the neck near the thyroid gland. This hormone helps in the role of regulating the levels of calcium and phosphate in the blood. If the calcium level is low in the blood, more parathormone is released into the bloodstream. They maintain the level of calcium by bone resorption, increasing the absorption of calcium from the intestine and decreasing the level of calcium that is excreted.

To determine the effects of Parathyroid hormone (PTH), we evaluate each given option:

1. Stimulates the process of bone resorption: PTH increases the activity of osteoclasts which breaks down bone tissue, releasing calcium into the bloodstream. This is a known effect of PTH.
2. Decreases Ca²⁺ level in blood: PTH actually increases calcium levels in the blood by stimulating bone resorption, enhancing renal reabsorption of calcium, and increasing intestinal absorption of calcium. Thus, this statement is not an effect of PTH.
3. Reabsorption of Ca²⁺ by renal tubules: PTH promotes renal calcium reabsorption, thus conserving calcium levels. This statement aligns with known PTH effects.
4. Decreases the absorption of Ca²⁺ from digested food: PTH increases calcium absorption from the intestine indirectly by promoting the formation of active vitamin D (calcitriol). Therefore, this is not an effect of PTH.
5. Increases metabolism of carbohydrates: PTH does not primarily influence carbohydrate metabolism. This is not a known effect of PTH.

Based on the analysis, the statements that are not effects of PTH are:

1. (b) Decreases Ca²⁺ level in blood
2. (d) Decreases the absorption of Ca²⁺ from digested food
3. (e) Increases metabolism of carbohydrates

The correct option is: (b), (d) and (e) only

C. Normal rhythm of sleep-wake cycle

• The sleep-wake cycle is primarily regulated by the hormone melatonin, which is produced by the pineal gland, not the thyroid gland.

D. Development of immune system

• The development and regulation of the immune system involve various factors, including immune cells, cytokines, and other immune-related molecules. The thyroid hormone itself does not have a direct role in the development of the immune system.

The other options are partially or directly influenced by thyroid hormone:

A. Maintenance of water and electrolyte balance

• Thyroid hormone can influence water and electrolyte balance by affecting kidney function and electrolyte transport.

B. Regulation of basal metabolic rate

• Thyroid hormone plays a significant role in regulating the basal metabolic rate (BMR) of the body.

E. Support the process of R.B.Cs formation

• Thyroid hormone is involved in erythropoiesis, the process of red blood cell formation. It affects the production and maturation of red blood cells in the bone marrow.

The correct option is (B): C and D only