Chemical Coordination and Integration

Exophthalmic goitre – hypersecretion of thyroid hormone and protruding eyeballs Acromegaly – excessive secretion of growth hormone (in adults) Cushing's syndrome – excess secretion of cortisol, moon face and hyperglycaemia Cretinism – hyposecretion of thyroid hormone (in infancy) and stunted growth Correct match: A-III, B-IV, C-I, D-II.

Cholecystokinin (CCK), a hormone secreted by I-cells of the upper small intestine. It acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzymes and bile juice, respectively. Gastric inhibitory peptide (GIP) is secreted by K-cells of the small intestine. It acts to decrease gastrin and gastrin dependent acid secretion from the parietal cells of the stomach (gastric glands). Atrial natriuretic factor (ANF) is a peptide hormone secreted by atrial wall of our heart. It decreases blood pressure. Anti-diuretic hormone (ADH) causes the kidneys to return more water to the blood and thus decrease the urine volume.

Glucocorticoids stimulate gluconeogenesis, lipolysis and proteolysis, increasing blood sugar level – correct. Glucagon is associated with hyperglycaemia, and insulin acts on hepatocytes and adipocytes and is associated with hypoglycaemia.

FSH is a peptide (lipid-insoluble) hormone, so it cannot pass through the membrane and acts through membrane-bound receptors - the assertion is correct. Binding of such hormones to membrane receptors generates second messengers (cAMP) - the reason is also correct, but it does not explain why FSH does not enter the cell (that is due to its lipid insolubility).

FSH is a protein hormone; it cannot enter the cell, so it first binds to specific membrane-bound receptors on the ovarian cell membrane and acts through a second messenger.
FSH stimulates follicular growth and estrogen secretion, not progesterone. Glucagon is secreted by α-cells. Thymosin secretion decreases with ageing as the thymus degenerates.

Steroid hormones are lipid soluble, so they pass easily through the plasma membrane of the target cell.
Inside the cell they bind to specific intracellular receptors, mostly nuclear receptors, to form a hormone-receptor complex.
This complex binds to a specific regulatory DNA sequence of the genome (the hormone response element).
The binding switches on the transcription of a particular set of genes one after another, so that mRNA and then proteins are produced. In this way steroid hormones regulate gene expression and chromosome function.
The steroid does not bind to mRNA, tRNA or the ribosome; these take part later in translation.
So the sequential expression of a set of genes occurs when the steroid molecule binds to the DNA sequence.

Epinephrine is known as the emergency hormone (A-IV); Thyroxine regulates the basal metabolic rate (B-III); Oxytocin causes smooth muscle contraction (C-II); Glucagon causes hyperglycemia (D-I).

Atrial Natriuretic Factor (ANF) is actually secreted by the atria of the heart, not the seminiferous tubules of the testes — so statement C is wrong. Gastrin acts on the gastric glands (not the intestinal wall) and stimulates secretion of HCl and pepsinogen — so statement E is also wrong.

Oxytocin and Vasopressin (ADH) are synthesised by the hypothalamus and stored/released from the neurohypophysis (posterior pituitary).

Pituitary hormone is of the peptides/proteins type (a-iii); Epinephrine is a biogenic amine (b-iv); Endorphins are neuropeptides (c-ii); Cortisol is a steroid (d-i).

Mature insulin consists of only two polypeptide chains, A and B (linked by disulphide bridges), not three chains — so the statement that it consists of three chains (A, B and C) is incorrect. Insulin is synthesised as a prohormone (proinsulin) containing an extra C-peptide segment, which is removed before the mature hormone is formed.

Thyrocalcitonin (TCT) regulates blood calcium levels (A is correct), and FSH along with androgens regulates spermatogenesis in males (B is correct). Hypothyroidism (not hyperthyroidism) typically leads to goitre (C is incorrect as stated). Glucocorticoids are secreted from the Adrenal Cortex, not the Adrenal Medulla (D is incorrect). Parathyroid hormone is regulated by circulating levels of calcium ions, not sodium ions (E is incorrect). So A and B only.

Parathyroid hormone (PTH) does act on bones to stimulate bone resorption, increasing blood calcium levels (Statement I is true). PTH and thyrocalcitonin together play a significant role in calcium metabolism (regulating blood calcium levels), not carbohydrate metabolism — so Statement II is false.

During pregnancy the metabolic rate of the mother increases to meet the needs of the mother and the developing foetus; this is brought about by an increase in thyroxine. Both statements are correct and the reason explains the assertion.

Estrogen promotes the activity of osteoblasts and inhibits osteoclasts. In an ageing female, osteoporosis occurs due to deficiency of estrogen. Parathormone promotes mobilisation of calcium from bone into blood. Excessive activity of parathormone causes demineralisation, leading to osteoporosis.

The ovary secretes estradiol, progesterone and inhibin. Inhibin is secreted by granulosa cells of ovarian follicles and the corpus luteum.
Its target is the anterior pituitary, where it inhibits the secretion of FSH.

Relaxin is secreted by the ovary during pregnancy; it helps parturition, softens the pubic symphysis and relaxes the cervix. Inhibin decreases the secretion of FSH and LH. They do not have opposite effects.

Certain substances in food (goitrogens, e.g., in cabbage and related vegetables) interfere with the uptake of iodine and the synthesis of thyroxine.
The fall in thyroxine removes the negative feedback on the pituitary, so more TSH is secreted; TSH makes the thyroid gland enlarge. This enlargement due to under-production of thyroxine is simple goitre.
Thyrotoxicosis and toxic (exophthalmic) goitre are conditions of over-secretion of thyroid hormones, i.e., hyperthyroidism.
Cretinism results from deficiency of thyroid hormones during pregnancy and infancy and causes stunted growth and mental retardation in the child.
Hence such toxic agents lead to simple goitre.

Deficiency of thyroid hormones is called hypothyroidism in general; its specific forms have separate names.
In adults, deficiency of thyroxine causes myxoedema: low basal metabolic rate, gain in body weight, puffy appearance due to retention of water (accumulation of mucopolysaccharides under the skin), lethargy and low body temperature.
Cretinism is the result of thyroid hormone deficiency in infants and children: stunted growth, mental retardation, low intelligence quotient and abnormal skin.
Simple goitre is the enlargement of the thyroid gland due to deficiency of iodine in the diet.
Since the question specifies adults and these three symptoms, the disorder is myxoedema.

Vasopressin (ADH) is synthesised in the hypothalamus but is stored in and released from the posterior pituitary; it stimulates reabsorption of water in the distal tubules of the nephron and so reduces loss of water in urine. This row is fully correct.
Thyroxine from the thyroid regulates the basal metabolic rate; blood calcium is regulated by thyrocalcitonin (and parathyroid hormone).
Oxytocin does cause contraction of the uterus during child birth, but it is released from the posterior pituitary, not the anterior pituitary.
The corpus luteum secretes mainly progesterone, which supports pregnancy.
Hence the correct match is posterior pituitary – vasopressin – stimulates resorption of water in the distal tubules.

In a negative feedback loop, a change in a controlled condition brings about responses that oppose the change and return the condition to its set point.
Body temperature is controlled by the thermoregulatory centre in the hypothalamus.
When it is too cold, the hypothalamus brings about constriction of the skin blood vessels (vasoconstriction), which reduces heat loss, and contraction of skeletal muscles (shivering), which produces heat.
The body temperature rises back to normal, and the responses then stop. This is a negative feedback loop.
When it is too hot, the correct responses are sweating and dilation (not constriction) of the skin blood vessels, so that statement is wrong as written.
Secretion of tears and salivation at the sight of food are reflex actions, not feedback loops.
So the example of a negative feedback loop is the constriction of skin blood vessels and contraction of skeletal muscles when it is too cold.

The adrenal cortex secretes steroid hormones called corticoids.
The corticoids that are involved in carbohydrate metabolism are called glucocorticoids; in humans, cortisol is the main glucocorticoid.
Cortisol stimulates gluconeogenesis, lipolysis and proteolysis, and inhibits the cellular uptake and utilisation of amino acids, so it raises the blood glucose level.
It is also involved in maintaining the cardiovascular system and kidney functions, and it produces anti-inflammatory reactions and suppresses the immune response.
Corticosterone and 11-deoxycorticosterone act mainly as mineralocorticoids in humans, regulating the balance of water and electrolytes.
Cortisone is a less active form derived from cortisol.
So the steroid hormone that regulates glucose metabolism is cortisol.

The duodenum is the first part of the small intestine. Its submucosa contains Brunner's glands, and its mucosa contains endocrine cells.
The duodenal mucosa produces two important gastrointestinal hormones:
Secretin: stimulates the pancreas to secrete a watery juice rich in bicarbonate, which neutralises the acidic chyme.
Cholecystokinin (CCK): stimulates the pancreas to secrete enzymes and the gall bladder to contract and release bile.
Prolactin, parathormone, estradiol and progesterone are produced by the pituitary, parathyroid and ovaries, not by the duodenum.
So the two duodenal hormones are secretin and cholecystokinin. (Strictly, Brunner's glands secrete an alkaline mucus, while these hormones come from endocrine cells of the duodenal mucosa; the question links them to the duodenum.)