The Pituitary Gland Questions in English

(A) Diabetes insipidus is a condition characterized by the excretion of large amounts of dilute urine (polyuria) and excessive thirst (polydipsia).
This occurs due to the deficiency of Anti-diuretic hormone $(ADH)$,also known as vasopressin.
$ADH$ is synthesized by the hypothalamus and stored and released by the posterior lobe of the pituitary gland (neurohypophysis).
Since the deficiency of $ADH$ leads to the symptoms described in the Assertion,the Reason correctly explains the physiological basis of the condition.

(A) Prolactin is unique among the anterior pituitary hormones because its secretion is primarily regulated by inhibitory control from the hypothalamus.
This inhibitory control is mediated by the neurotransmitter dopamine,which acts as the Prolactin Inhibiting Hormone $(PIH)$.
Dopamine is synthesized and released by the tuberoinfundibular neurons in the hypothalamus,which then travels through the hypophyseal portal system to inhibit the lactotrophs in the anterior pituitary.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for the Assertion.

(C) Oxytocin stimulates the contraction of uterine muscles during childbirth and initiates the ejection of milk from the mammary glands.
Oxytocin is synthesized in the hypothalamus and transported to the posterior pituitary gland (neurohypophysis) for storage and release.
Therefore,the Assertion is correct,but the Reason is incorrect because the posterior pituitary does not synthesize oxytocin; it only stores and releases it.

(B) Oxytocin is a hormone secreted by the neurohypophysis (posterior pituitary) of the pituitary gland.
It acts on the smooth muscles of the uterus and stimulates their vigorous contraction,which is essential for the process of parturition (childbirth) and the induction of labour pain.

(D) Oxytocin is known as the milk-ejecting hormone because it stimulates the contraction of the smooth muscles (myoepithelial cells) of the mammary glands,which leads to the ejection of milk. Prolactin,on the other hand,is responsible for the production of milk.

(D) The Assertion is incorrect because the synthesis of milk is stimulated by the hormone $Prolactin$,not oxytocin. Oxytocin is responsible for the ejection of milk (milk let-down reflex).
The Reason is incorrect because oxytocin is synthesized by the hypothalamus and stored/released from the $Neurohypophysis$ (posterior pituitary),not the $Adenohypophysis$ (anterior pituitary).

(A) The pituitary gland is anatomically divided into an adenohypophysis and a neurohypophysis.
The adenohypophysis consists of two portions: $Pars \text{ } distalis$ and $Pars \text{ } intermedia$.
The $Pars \text{ } distalis$ region of the pituitary is commonly called the anterior pituitary.
It produces several important hormones such as Growth Hormone $(GH)$, Prolactin $(PRL)$, Thyroid Stimulating Hormone $(TSH)$, Adrenocorticotrophic Hormone $(ACTH)$, Luteinizing Hormone $(LH)$, and Follicle Stimulating Hormone $(FSH)$.

(A) Prolactin is a hormone secreted by the anterior pituitary gland. Its primary function is to stimulate the growth and development of mammary glands and to promote the production and secretion of milk in them. Therefore,it is also known as the lactogenic hormone.

(A) In the given diagram:
$P$ represents the Hypothalamus,which is the basal part of the diencephalon.
$Q$ represents the Anterior pituitary (Adenohypophysis),which is connected to the hypothalamus through a portal circulatory system.
$R$ represents the Posterior pituitary (Neurohypophysis),which is under the direct neural regulation of the hypothalamus.
Therefore,the correct sequence is $P$ = Hypothalamus,$Q$ = Anterior pituitary,$R$ = Posterior pituitary.

(B) $LH$ stands for Luteinizing Hormone.
It is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland.
Its primary site of action is the gonads (testes in males and ovaries in females).
In males,$LH$ acts on the Leydig cells to stimulate the synthesis and secretion of androgens.
In females,$LH$ induces ovulation of fully mature follicles (Graafian follicles) and maintains the corpus luteum.

(C) $1$. Oxytocin acts on the smooth muscles of our body and stimulates their contraction. In females,it stimulates a vigorous contraction of the uterus at the time of child birth,and milk ejection from the mammary gland. Prolactin regulates the growth of the mammary gland.
$2$. $ACTH$ (Adrenocorticotropic hormone) stimulates the synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex,not mineralocorticoids.
$3$. Vasopressin,also known as Antidiuretic Hormone $(ADH)$,acts mainly at the kidney and stimulates the reabsorption of water and electrolytes by the distal tubules and thereby reduces loss of water through urine (diuresis).
$4$. Parathyroid hormone $(PTH)$ increases the $Ca^{2+}$ levels in the blood by acting on bones and stimulating the process of bone resorption (dissolution/demineralization).

(B) Gonadotropic hormones, also known as gonadotropins, are hormones secreted by the anterior pituitary gland that act on the gonads (testes or ovaries) to regulate their growth and function.
These hormones include $Luteinizing \text{ } Hormone$ $(LH)$ and $Follicle \text{ } Stimulating \text{ } Hormone$ $(FSH)$.
$LH$ and $FSH$ stimulate the production of sex hormones and the maturation of gametes in both males and females.
Therefore, option $B$ is the correct answer.

(C) Vasopressin,also known as Antidiuretic Hormone $(ADH)$,is released by the posterior pituitary gland.
It acts primarily on the kidney tubules to facilitate the reabsorption of water and electrolytes into the blood.
By increasing water reabsorption,it reduces the volume of water excreted in the urine (making urine more concentrated).
Additionally,$ADH$ causes the constriction of blood vessels,which leads to an increase in blood pressure.

(B) The pituitary gland,often called the master gland,releases hormones into the bloodstream.
Specifically,the hormones secreted by the anterior pituitary are transported via the $Hypophyseal$ $portal$ $vein$ system.
This specialized vascular system connects the hypothalamus to the anterior pituitary,allowing for the direct transport of regulatory hormones.
Therefore,the $Hypophyseal$ $portal$ $vein$ is the primary structure that receives these hormones to facilitate their distribution.

(A) Statement $I$ is correct: Growth hormone $(GH)$,also known as somatotropin,is secreted by the anterior pituitary gland. Its levels are highest during childhood and adolescence,peaking during puberty to facilitate rapid body growth.
Statement $II$ is correct: Even after puberty,$GH$ continues to be secreted throughout life,although at lower levels. It plays a crucial role in metabolic processes,protein synthesis,and the repair and replacement of cells in various tissues.

(B) $Diabetes \text{ } insipidus$ is a condition caused by the deficiency of $Antidiuretic \text{ } Hormone$ $(ADH)$, also known as $vasopressin$.
$ADH$ is secreted by the posterior pituitary gland and acts on the kidney tubules to facilitate the reabsorption of water.
When $ADH$ levels are low, the kidneys cannot reabsorb water efficiently, leading to the excretion of large volumes of dilute urine (polyuria) and a constant feeling of excessive thirst (polydipsia).

(B) Acromegaly is a condition caused by the hypersecretion of Growth Hormone $(GH)$ in adults.
In adults,the epiphyseal plates are closed,so the bones cannot grow in length.
Instead,the excess $GH$ causes the bones of the face,hands,and feet to thicken and enlarge,leading to the characteristic features of acromegaly.
$ACTH$ is Adrenocorticotropic Hormone,$MSH$ is Melanocyte-Stimulating Hormone,and $TSH$ is Thyroid-Stimulating Hormone,none of which are responsible for acromegaly.

(C) is the correct answer.
The neurohypophysis (posterior pituitary) stores and releases oxytocin and vasopressin.
These hormones are synthesized in the hypothalamus and transported axonally to the neurohypophysis,where they are stored and later released into the bloodstream.

(D) Prolactin.
$Prolactin$ is a hormone secreted by the anterior pituitary gland in both males and females.
Its primary function is to stimulate the growth of mammary glands and the production of milk in females after childbirth.
While it is present in males,it does not have a known physiological function in the male reproductive system,making it functional only in females.