` ENDOCRINE PHYSIOLOGY PART 2: PITUITARY GLAND–DR. BARBON LEA THERESE R. PACIS 1 ENDOCRINE PHYSIOLOGY PART 2: PITUITARY GLAND Dr. Felipe Barbon I.ANTERIOR PITUITARY GLAND (ADENOHYPOPHY SIS) Types of Adenohypophyseal Cells Staining Characteristics -Granular Acidophils (40%)–Growth Hormone, Prolactin Basophil s (10%) –Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Thyroid Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH) -Agranular Chromophobes–Adrenocorticotropic Hormone (ACTH) Secretory Activity -Somatotropes –Growth Hormones (GH)/Somatotropin (STH); about 50% -Lactotropes (Mammosomatotropes)–Prolactin (PRL); 10-25% -Thyrotropes –Thyroid Stimulating Hormone (TSH); <10% -Gonadotropes –Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH); 10-15% -Corticotropes (POMC Cells -- Pro-opiomelanocort in Cells) –Adrenocorticotropic Hormones (ACTH) and β-Lipotropic Hormone (β-LPH); 15-20% -Mammosomatotropes –Growth Hormone (GH), Prolactin (PRL) A.GROWTH HORMONE Growth Hormone Polypeptide (191 Amino Acid Residues) Specie specificUses cytokine receptors (JAK2 and STATs) -STAT = Signal Transducer and Activator of Transcription Also known as SOMATOTROPIN (STH)Half-life = 6-20 minutes (20-50 minutes) Plasma level higher in infants and children than adults The activity of both Anterior and Posterior Pituitary Gland is controlled by the hypothalamus. The Pituitary Gland is connected to the hypothalamus through the INFUNDIBULUM(also called the HYPOTHALAMO-HY POPHYSEAL STALK). Hypothalamic neurons, present in the hypothalamus, are connected to the ANTERIOR PITUITARY GLAND(Adenohypophysis) through the blood vessels present in the stalk. To control the Anterior Pituitary Gland, the hypothalamic neurons utilizes chemical agents (called HORMONES), both Releasing and Inhibitory Hormones. These hormones are released directly into the circulation. Human Growth Hormone can only promote growth to humans. Release of growth hormones is not continuous, it released in a pulsatile manner. After puberty, there is a marked decrease in hormone production –that is why there is minimal growth seen in adults. On the other hand, to control the POSTERIOR PITUITARY GLAND, the hypothalamus will now use the neurons present in the stalk. The hypothalamus will not utilize hormones but instead, it will generate nerve impulses. It will be the nerve impulse coming from the hypothalamus that will affect the activity of the Posterior Pituitary -- that is why it is called Neurohypophysis, because it is neurally controlled.
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[PhysioB] Endocrine Physiology Part 2 - Pituitary Gland - Dr. Barbon (Lea Pacis)
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8/12/2019 [PhysioB] Endocrine Physiology Part 2 - Pituitary Gland - Dr. Barbon (Lea Pacis)
- STAT = Signal Transducer and Activator of Transcription
Also known as SOMATOTROPIN (STH)
Half-life = 6-20 minutes (20-50 minutes)
Plasma level higher in infants and children than adults
The activity of both Anterior and
Posterior Pituitary Gland is controlled by
the hypothalamus. The Pituitary Gland is
connected to the hypothalamus through
the INFUNDIBULUM (also called theHYPOTHALAMO-HYPOPHYSEAL STALK).
Hypothalamic neurons, present in the
hypothalamus, are connected to the
ANTERIOR PITUITARY GLAND
(Adenohypophysis) through the blood
vessels present in the stalk. To control
the Anterior Pituitary Gland, the
hypothalamic neurons utilizes chemical
agents (called HORMONES), both
Releasing and Inhibitory Hormones.
These hormones are released directly
into the circulation.
Human Growth Hormone can only promote growth to humans.
Release of growth hormones is not continuous, it released in a pulsatile manner.
After puberty, there is a marked decrease in hormone production –that is why there
is minimal growth seen in adults.
On the other hand, to control the POSTERIOR PITUITARY GLAND, the hypothalamus will now usethe neurons present in the stalk. The hypothalamus will not utilize hormones but instead, it will
generate nerve impulses. It will be the nerve impulse coming from the hypothalamus that will
affect the activity of the Posterior Pituitary -- that is why it is called Neurohypophysis, because it
is neurally controlled.
8/12/2019 [PhysioB] Endocrine Physiology Part 2 - Pituitary Gland - Dr. Barbon (Lea Pacis)
` ENDOCRINE PHYSIOLOGY PART 2: PITUITARY GLAND –DR. BARBON
LEA THERESE R. PACIS 5
Dwarfism (Non-Endocrine Disorders)
- Malnutrition
- Syndromes of short stature (Turner’s)
- Autosomal Chromosomal Disorders (Down’s)
- Chronic Cardiac/Pulmonary Disorders
- GI/Hepatic/Renal Disorders
- Achondroplasia – Autosomal dominant condition wherein there is alteration in fibroblas
growth factor receptor
- Kaspar-Hauser Syndrome – pyschosocial dwarfism; seen in neglected and chronically abusedchildren
B. MELANOCYTE STIMULATING HORMONE (MSH)
Melanocyte Stimulating Hormone (MSH)
Stimulates the melanocytes to produce melanin Evenly distributed
Adrenocorticotropic Hormone (ACTH) = Hormone with melanocyte stimulating effect- When present in excessive amount in the blood, skin pigmentation occurs
Abnormal Skin Pigmentation/Lack of Pigmentation
Albinism – congenital absence of melanin
Piebaldism – congenital defect characterized by patches of skin that lacks melanin
Pituitary Failure (Hypopituitarism)
Decrease in the secretion:
- Gn (FSH/LH) Mild cases
- TSH Mild to moderate
- ACTH Moderate to severe
- GH (STH) Severe cases
II. POSTERIOR PITUITARY GLAND (NEUROHYPOPHYSIS)
Neurohypophyseal Hormones
Produced as prehormones
Cosecreted with a peptide – Neurophysin
Neurophysin I = associated with ADH
Neurophysin II = associated with Oxytocin
A. ANTI-DIURETIC HORMONE (ADH) or ARGININE VASOPRESSIN (AVP)
Anti-Diuretic Hormone (ADH) or Arginine Vasopressin (AVP) Short polypeptide, 9 Amino Acid residue
Uses the following receptors:
- V1a and V1b = Vasoconstrictive Effects (PI Ca++)
- V2 = Anti-Diuretic Effects (G-Protein cAMP)
Half-life = 15-20 minutes
Essential for water balance
Affects facultative water reabsorption in the kidneys [Late Part of the Distal Convoluted Tubules
and Cortical Collecting Ducts] (Water channels – AQP2)
Excitatory Stimuli for ADH Release:
Increase Effective PCOP (OPPP)
- 1% increase in plasma osmolarity
Dehydration (Nausea, Vomiting, Diarrhea)
Hypovolemia
- 5-10% decrease in blood volume Pain
Emotion
Stress
Exercise
Warm/Hot Environment
Standing
Angiotensin
Nicotine, Clofibrate, Carbamazepine
Inhibitory Stimuli for ADH:
Decrease effective PCOP (OPPP)
Overhydration
Hypervolemia
Alcohol Intake
Cool/Cold Environment
Regulation of Secretion and Actions of ADH:
Before, they say that there is such thing as “Melanocyte Stimulating Hormone (MSH),” and
say that it is responsible for skin pigmentation. But now they found out that there is none.
Now, they say that the one stimulating the melanocytes to produce melanin is having a
normal amount of Adrenocortitropic Hormone (ACTH). ACTH has a melanocyte stimulating
effect.
Degree of pigmentation does not depend on the amount of ACTH, depends on
the number of melanocytes present in your skin
Lighter Skin: melanocytes
Darker Skin: melanocytes
Melanocytes protects the skin from UV rays
melanocytes More prone to skin cancer
ACTH will have a different effect on the body with regards to pigmentation
There will still be pigmentation, but it is not evenly distributed
Your skin is not the only one affected, even your mucosa is affected
Degree of severity of injury in the Pituitary Gland depends on the activity of the Anterior
Pituitary Gland, particularly to the amount of secretions.
Receptors for plasma osmolality
Located in the OrganumVasculosum of the Lamina
Terminalis
Volume sensitive receptors
Located in the Subfornical Organs
Thirst Center Superolateral
Part of the Hypothalamus,
specifically in the median preoptic
nucleus
8/12/2019 [PhysioB] Endocrine Physiology Part 2 - Pituitary Gland - Dr. Barbon (Lea Pacis)