Write short notes on the functions of the following hormones

(a) Parathyroid hormone (PTH)

1. It is a peptide hormone which is secreted by the parathyroid gland

2. The circulating levels of calcium ions regulates its secretion

3. The levels of calcium ions in the blood is increased by PTH.

4. The bone resorption process is triggered by PTH.

5. The reabsorption of calcium ions by the renal tubules is triggered which increases calcium ions absorption from the food that is digested

6. PTH is a hypercalcemic hormone which increases the blood Ca2+ levels

7. It has a critical role to play in balancing calcium in the body along with TCT, i.e., in calcium homeostasis.

(b) Thyroid hormones Thyroxine/tetraiodothyronine(T₄)

1. This hormone checks the basal metabolic rate (BMR) and body growth such as mental development and ossification of bones

2. The body weight is controlled.

3. It controls the tissue differentiation and metamorphosis of tadpole larva into an adult frog

4. Formation of RBC is suppressed

5. Tri-iodothyronine(T₃) – The energy consumption and body’s oxygen are increased. It also increases heart rate and force of contraction which inturn increases the cardiac output

(c) Thymosin

1. The differentiation of T-lymphocytes is triggered which provides cell-mediated immunity

2. The antibody production is facilitated to provide humoral immunity

3. The rate of division of cell in children is triggered thereby promotes growth

(d) Androgens

1. The interstitial cells located in the intertubular space generate a collection of hormones called as androgens, testosterone mainly

2. Checks the maturation, development and functions of the male accessory sex organs such as epididymis, vas deferens, urethra, seminal vesicles, prostate gland etc.

3. These trigger the growth of facial and axillary hair, muscles, aggressiveness, low pitch of voice etc.

4. In the phenomena of spermatogenesis, these play a critical stimulatory role

5. They act on the central neural system which influences the male sexual behavior

6. They generate anabolic effects on carbohydrate metabolism and protein

(e) Estrogen

1. It triggers the development of ovarian follicles and the growth & development of the female reproductive organs namely the fallopian tube, uterus and vagina

2. It causes the LH secretion to increase and FSH secretion to decrease

3. The sensitivity of the uterus to the hormone – oxytocin is enhanced

4. The development of mammary gland is facilitated

5. The female sexual behavior is regulated.

(f) Insulin

1. Glucose homeostasis is regulated

2. It acts on hepatocytes and adipocytes

3. The transport of glucose to the muscles from blood is triggered

4. The oxidation of glucose is facilitated and brings about glycogenesis, i.e., the conversion of glucose to glycogen causing hyperglycemia

Glucagon

1. It is critical in maintaining normal blood glucose levels

2. Acts on hepatocytes which triggers the conversion of glycogen to glucose

3. The gluconeogenesis phenomena is triggered i.e., the conversion of non-carbohydrate particles namely – proteins and fats to glucose