Pituitary and Thyroid MCQs

In SIADH, to prevent the overactivity of ADH, Kidney adapts by down regulating the production and insertion of Aquaporin-2 channel proteins Reference: Ganong, 25th edition page no.696

Cytokine receptors (JAK - STAT) serves as receptors for, Growth hormone Prolactin Erythropoietin Leptin Reference: Ganong 25th edition page No.56

Oxytocin plays an especially important role in lactation-a role that is far better understood than its role in delivery. In lactation, oxytocin causes milk to be expressed from the alveoli into the ducts of the breast so that the baby can obtain it by suckling. Actions of oxytocin Contraction of myoepithelial cells in the breast Milk is forced from the mammary alveoli into the ducts and ejected. Contraction of the uterus During pregnancy, oxytocin receptors in the uterus are up-regulated as parturition approaches, although the role of oxytocin in normal labor is uncertain. Oxytocin can be used to induce labor and reduce postpartum bleeding. Option a) prolactin: responsible for galactopoiesis Option c) ductular proliferation of breast

Hormones that Use Receptor Tyrosine Kinase Signalling. Growth Hormone Insulin Leptin Prolactin Growth Factors

Answer- A. Decrease cerebral growth is 'a' i.e., Decrease cerebral growth [Ref : Ghai 7h/e p. 481; Jornal of Americal Physiological Review] Thyroid hormone has major effect on brain in utero & neonatal period, deficiency cause diminsh axonal growth, dendritic arborisation, delay proliferation & migration of granule cell so it decrease cerebral growth.

Explanation: The mechanism is similar because both processes are mediated by oxytocin-induced contraction of smooth muscle . During labor, oxytocin stimulates contractions of the myometrium (uterine muscle). During breastfeeding, it stimulates contractions of the myoepithelial cells in the breast. Explanation of other options: Water retention by ADH (Option B): ADH (vasopressin) acts on renal tubules to increase water permeability, a mechanism not involving smooth muscle contraction. FSH secretion by anterior pituitary (Option C): FSH secretion is regulated by hypothalamic GnRH and involves endocrine feedback loops, not smooth muscle contraction. Key Takeaways: Oxytocin's primary action is to stimulate smooth muscle contraction in the uterus and breasts. This is a classic example of a single hormone having similar effects on different tissues.

ACTH is inhibited by cortisol as a part of negative feedback Reference: Ganong, 25th edition page no.366

In humans, prolactin secretion is increased by exercise, surgical and psychological stresses, and stimulation of the nipple. The plasma prolactin level rises during sleep, the rise starting after the onset of sleep and persisting through out the sleep period. Secretion is increased during pregnancy, reaching a peak at the time of parturition. After delivery, the plasma concentration falls to nonpregnant levels in about 8 days. Suckling produces a prompt increase in secretion, but the magnitude of this rise gradually declines after a woman has been nursing for more than 3 months. With prolonged lactation, milk secretion occurs with prolactin levels that are in the normal range.