A polypeptide hormone Calcitonin (CT) is produced by parafollicular cells of _________ gland.

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Correct — option (3), Thyroid. The word 'parafollicular' settles the question on its own. The thyroid is the one gland in the body that is built out of follicles: hollow spherical sacs whose lining cells (the follicular cells) trap iodine and manufacture the thyroid hormones thyroxine (T4) and tri-iodothyronine (T3). Scattered between and around those follicles is a second, quite separate cell population — the parafollicular cells, also called C cells, 'para-' meaning beside the follicle. These C cells secrete calcitonin, a polypeptide hormone of 32 amino acids. Calcitonin lowers the level of calcium in the blood: it damps down the bone-dissolving activity of osteoclasts, so less calcium is released from bone into the circulation, and it reduces the reabsorption of calcium in the kidney tubules, so more is lost in urine. It is therefore the functional opposite of parathyroid hormone (PTH), secreted by the four parathyroid glands sitting on the back of the thyroid, which raises blood calcium. The gland is anatomically one thing with two hormone-making jobs, and a candidate who remembers only 'thyroid = thyroxine' misses the second. Note also that the thyroid gland is a bilobed endocrine gland lying on either side of the trachea, the two lobes joined by a connecting band called the isthmus.

Why the other options are wrong — (a) The salivary glands are exocrine, not endocrine: they pour their secretion through ducts into the mouth rather than into the blood. Humans have three pairs — parotid, sub-maxillary/sub-mandibular and sub-lingual — and what they secrete is saliva, containing the starch-splitting enzyme salivary amylase (ptyalin) along with lysozyme, mucus and electrolytes. There is no follicular architecture in a salivary gland and therefore nothing that could be called a parafollicular cell, and salivary tissue produces no hormone that circulates in the blood.  (b) Sweat glands are exocrine glands of the skin, embedded in the dermis and opening at the body surface through a pore. Their secretion is a watery fluid whose evaporation cools the body, and which also carries away small amounts of salt, urea and lactate. Like the salivary glands they are ducted, they have no follicles, and they release nothing into the bloodstream. Sweat glands appear in the syllabus under thermoregulation and skin structure, never under the endocrine system.  (d) This is the trap worth taking seriously, because the pancreas genuinely is a hormone factory and its hormones genuinely are polypeptides. It is a composite gland: the exocrine part secretes pancreatic juice, and the endocrine part — the islets of Langerhans — secretes insulin from the beta cells and glucagon from the alpha cells, both peptides. But the islet is not a follicle, so the pancreas has no parafollicular cells; and the pancreatic hormones regulate blood glucose, not blood calcium. Two words in the stem, 'parafollicular' and 'Calcitonin', each independently rule the pancreas out.

Concept: Blood calcium is held inside a narrow range by a push-pull pair of hormones, and the syllabus expects you to hold both halves. Parathyroid hormone (PTH, parathormone) comes from the four parathyroid glands on the posterior surface of the thyroid; it is hypercalcaemic, raising blood calcium by promoting the dissolution of bone matrix by osteoclasts, by increasing calcium reabsorption in the kidney tubules and by increasing absorption of calcium from the food in the gut. Calcitonin comes from the thyroid's parafollicular cells; it is hypocalcaemic, pulling blood calcium down by exactly the opposite routes. Calcium matters far beyond the skeleton — it is required for muscle contraction, for the transmission of the nerve impulse at the synapse and for blood clotting — so this pair is the body's guarantee that those processes keep working whatever the diet supplies on a given day.

State PCS 2026 Q62 — Science & Technology PYQ with Answer

State PCS 2026 Q62 — Science & Technology PYQ with Answer