Endocrine glands and their hormones play a critical role in regulating many physiological processes in the human body, such as growth, metabolism, reproduction, and homeostasis. Therefore, understanding the anatomy, physiology, and pathology of endocrine glands is crucial for medical professionals, including those who will be taking the NEET PG exam.
Endocrine-related questions are frequently tested in the exam, making it important for candidates to have a good grasp of this topic.
It has got glandular elements so it is called adenohypophysis
Cells in the anterior pituitary are
These constitute 50% of the anterior pituitary cells
They do not attract any color / stain
They constitute the rest 50% of the anterior pituitary cells.
They attract some stains
These cells are further divided into two types
These cells constitute 70% of the chromophyl cells
These cells attract the acidic stain
They synthesize two hormones: GH & Prolactin
These are further divided into two parts:
These cells help in GH synthesis
They comprise of almost 50% of the acidophil cells
These cells are mainly for prolactin synthesis
They comprise almost 15-20% of acidophil
These cells attract basic stains
They constitute around 20-30% of the chromophyl cells
They synthesize the following hormones:
It has neural elements because of which it is called neurohypophysis
Hormones of posterior pituitary are:
These hormones are synthesized in the hypothalamic neurons.
The nuclei where they are synthesized are supra optic nucleus (for ADH) & paraventricular nucleus (for Oxytocin).
Now let us discuss all the hormones of Anterior Pituitary and Posterior Pituitary individually.
Anterior Pituitary hormones
All anterior pituitary hormones are controlled by hypothalamic factors or hormones, EXCEPT, “prolactin”.
For e.g. GH is controlled by GH inhibiting hormone called Somatostatin
Following are the major anterior pituitary hormones
GH (Growth Hormone)
GH is an anti-Insulin, diabetogenic hormone
GH performs two types of function:
Metabolic functions of GH can be studied w.r.t. carbohydrates, proteins & fats that are discussed below:
Growth Hormones & Carbohydrates
GH is a hyperglycemic hormone. It causes hyperglycemia by preventing the peripheral utilization of glucose. In that way GH is acting upon exogenous glucose.
As GH is diabetogenic, it results in Pituitary diabetes because of excessive GH secretion.
Growth Hormone & Protein synthesis
GH does not allow the protein breakdown as it promotes growth, rather it causes protein synthesis.
Growth hormone action on fats
GH causes breakdown of triglycerides. Therefore, it increases FFA (Free Fatty Acids) levels in the plasma.
Non-Metabolic functions of growth hormones
GH causes somatic growth.
Somatic growth means, the growth initiated by the action of mediators called Somatomedin or IGFs.
Disorders of growth hormones
Disorders of GH can be caused by either excess or deficiency of GH. Both of them are discussed below:-
Excess of GH before puberty can lead to Gigantism.
Excess of GH after puberty will lead to Acromegaly.
Deficiency of GH
Deficiency of GH before puberty leads to Dwarfism.
Dwarfism is of three types :-
Pituitary dwarf: These individuals have an absolute lack of GH before puberty.
Levi- Lorain dwarfism: In this, the GH is normal but there is a deficiency of Somatomedin C (IGF I).
Normal or increased GH dwarfism (Laron’s dwarfism): It is due to normal or increased GH but resistance to GH action (GH receptor insensitivity).
Regulation of GH secretion
The stimulators of GH are :-
The inhibitors of GH are:
GH – IH
Posterior Pituitary hormones
ADH results into two actions
Water reabsorption from Renal tubules
It is mediated by a V1 receptor.
It is mediated by V2 receptors
It happens when ADH binds with the V2 receptor in the collecting duct, there are insertions of channels called Aqua-porins II (AQP II) that results in reabsorption of water in the collecting duct.
These are the proteins which bind ADH & Oxytocin and carry them down to the posterior pituitary gland.
These are the bulb like bodies released from the axonal endings in the posterior pituitary.
It is involved in the positive feedback mechanism and neuroendocrine reflex.
Oxytocin performs the following important functions:
Milk ejection by contraction of the Myo-Epithelial cells of the breast.
Parturition i.e. the delivery of a baby.
Luteolysis i.e. degeneration of the corpus luteum.
It is the reflex for which afferent limb is neuron and efferent limb is hormonal.
For e.g. milk ejection.
To learn about the endocrine glands in detail watch the video lectures available on the PrepLadder app.
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