Endocrinology Flashcards
Origins of ant. And pst. Pituitary gland
Ant. Ectodermal, Phrngeal ectoderm ranke pouch
Pst. Neuro ectoderm as a downward diverticulum
Hormones from hypothalamus are transported to
anterior pituitary through
hypothalamo-hypophysial portal
blood vessels
the hormones from hypothalamus
to posterior pituitary are transported by
nerve fibers of
hypothalamo-hypophyseal tract
Anterior pituitary is also known as the master gland
because
it regulates many other endocrine glands
through its hormones
Parts of ant. Pituitary gland
- Pars distalis
- Pars tuberalis
- Pars intermedia
Anterior pituitary has two types of cells which are?
Functions
Chromophobe cells
2. Chromophil cells.
Chromophobe cells are not secretory in nature( no granules), but are the precursors of chromophil cells
50% Chromophil Cells and 50% Chromophobe are located in ant. Pituitary gland
Types of Chromophil cells based on staining property and secretary nature
i. Acidophilic cells or alpha cells, which form 35%
ii. Basophilic cells or beta cells, which form 15%.
Somatotropes
Corticotropes
Thyrotropes
Gonadotropes
Lactotropes
What are the function of Chromophil cells
i. Somatotropes, which secrete growth hormone
ii. Corticotropes, which secrete adrenocorticotropic
hormone
iii. Thyrotropes, which secrete thyroid-stimulating
hormone (TSH)
iv. Gonadotropes, which secrete follicle-stimulating
hormone (FSH) and luteinizing hormone (LH)
v. Lactotropes, which secrete prolactin.
Among the Chromophil cells which is Acidophil and Basophil?
Somatotropes and lactotropes are acidophilic cells,
whereas others are basophilic cells.
Somatotropes form
about 30% to 40% of the chromophil cells
Hypothalamus controls anterior pituitary by secreting
the releasing and inhibitory hormones (factors), which
are called neurohormones
Releasing and Inhibitory Hormones
Secreted by Hypothalamus
- Growth hormone-releasing hormone (GHRH):
Stimulates the release of growth hormone - Growth hormone-releasing polypeptide (GHRP):
Stimulates the release of GHRH and growth hormone - Growth hormone-inhibitory hormone (GHIH) or
somatostatin: Inhibits the growth hormone release - Thyrotropic-releasing hormone (TRH): Stimulates
the release of thyroid stimulating hormone - Corticotropin-releasing hormone (CRH): Stimulates
the release of adrenocorticotropin - Gonadotropin-releasing hormone (GnRH): Stimulates the release of gonadotropins, FSH and LH
- Prolactin-inhibitory hormone (PIH): Inhibits prolactin
secretion. It is believed that PIH is dopamine.
HORMONES SECRETED BY
ANTERIOR PITUITARY
- Growth hormone (GH) or somatotropic hormone
(STH) - Thyroid-stimulating hormone (TSH) or thyrotropic
hormone - Adrenocorticotropic hormone (ACTH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH) in females or interstitialcell-stimulating hormone (ICSH) in males
- Prolactin.
Recently, the hormone β-lipotropin is found to be
secreted by anterior pituitary
Among the hormones secreted by ant. Pituitary gland which is Tropic Hormones
GH
TSH
LH
ACTH
FSH
Growth hormone is secreted by
somatotropes which are
the acidophilic cells of anterior pituitary.
What’s the half life of GH
And where is it degraded
Half-life of circulating growth hormone is about 20
minutes. It is degraded in liver and kidney.
What’s the function of GH on the metabolism of all the three
major types of foodstuffs in the body
And other functions
GH increases the synthesis of proteins, mobilization of
lipids and conservation of carbohydrates.
GH increases the growth of the skeleton. It
increases both the length as well as the thickness of
the bones.
GH acts on bones, growth and protein metabolism
through
somatomedin secreted by liver
Types of Somatomedins
And their function
i. Insulin-like growth factor-I (IGF-I), which is also
called somatomedin C
ii. Insulin-like growth factor-II.
Somatomedin C (IGF-I) acts on the bones and
protein metabolism. Insulin-like growth factor-II plays
an important role in the growth of fetus.
Somatomedin C acts through the second messenger
called cyclic AMP
Regulation of GH Secretion is controlled by
hypothalamus and feedback mechanism
Hypothalamus regulates GH secretion via three hormones: which are?
GHRH
GHRP
GHIH or Somatostatin is also secreted by delta cells of islets
of Langerhans in pancreas
GH secretion is under negative feedback control
(Chapter 4). Hypothalamus releases GHRH and GHRP,
which in turn promote the release of GH from anterior
pituitary. GH acts on various tissues. It also activates
the liver cells to secrete somatomedin C (IGF-I).
Now, the somatomedin C increases the release
of GHIH from hypothalamus. GHIH, in turn inhibits the
release of GH from pituitary. Somatomedin also inhibits
release of GHRP from hypothalamus. It acts on pituitary
directly and inhibits the secretion of GH
GH inhibits its own secretion by stimulating the
release of GHIH from hypothalamus. This type of
feedback is called short-loop feedback control
Ghrelin promotes secretion of
GH by stimulating somatotropes directly.
In males, FSH acts along with
along with testosterone and
accelerates the process of spermeogenesis
In females FSH does
conversion of androgens into estrogen
development of graafian follicle from
primordial follicle
Stimulates the theca cells of graafian follicle and
causes secretion of estrogen
Actions of LH in male and female
In males, LH is known as interstitial cell-stimulating
hormone (ICSH) because it stimulates the interstitial
cells of Leydig in testes. This hormone is essential for
the secretion of testosterone from Leydig cells
nduces synthesis of androgens from theca cells of
growing follicle
3. Is responsible for ovulation
4. Is necessary for the formation of corpus luteum
5. Activates the secretory functions of corpus luteum
Prolactin acts directly on the epithelial cells of mammary glands and
causes localized alveolar hyperplasia.
Posterior pituitary consists of three parts:
Pars nervosa or infundibular process
2. Neural stalk or infundibular stem
3. Median eminence
Pars tuberalis of anterior pituitary and the neural
stalk of posterior pituitary together form the hypophyseal
stalk.
Actually, the posterior pituitary does not secrete any
hormone. ADH and oxytocin are synthesized in the
hypothalamus. From hypothalamus, these two hormones
are transported to the posterior pituitary through nerve fibers of hypothalamo-hypophyseal tract by means of
by means of axonic flow
the binding proteins which transport
ADH and oxytocin from hypothalamus to posterior
pituitary via hypothalamo-hypophyseal tract is
Neurophysin I
And
neurophysin II
Antidiuretic hormone (ADH) is secreted mainly by
supraoptic nucleus of hypothalamus. It is also secreted
by paraventricular nucleus in small quantity.
Potent stimulants for ADH secretion are:
- Decrease in the extracellular fluid (ECF) volume
- Increase in osmolar concentration in the ECF.
Oxytocin is secreted mainly by
And in small amount by?
paraventricular nucleus
of hypothalamus. It is also secreted by supraoptic
nucleus in small quantity
Throughout labor, large quantity of oxytocin is
released by means of _____ feedback mechanism,
positive
Examples of neuroendocrine reflex
Milk ejection reflex
Oxytocin in pregnant uterus contractions
Contraction of the uterus during sex
Sensitivity of uterus to oxytocin is accelerated by
_______ and decreased by _______
estrogen
progesterone
Possible cause of acromegaly and Gigantism
Hypersecretion of GH is because of tumor of acidophil
cells in the anterior pituitary
Possible cause of HYPOACTIVITY OF ANTERIOR PITUITARY
Tumor of chromophobes
Deficiency of GH-releasing hormone secreted
by hypothalamus
Deficiency of somatomedin C
iv. Atrophy or degeneration of acidophilic cells in
the anterior pituitary
iv. Panhypopituitarism:
HYPERACTIVITY OF POSTERIOR PITUITARY causes
Syndrome of Inappropriate Hypersecretion
of Antidiuretic Hormone (SIADH
Syndrome of Inappropriate Hypersecretion
of Antidiuretic Hormone (SIADH symptoms
- Loss of appetite
- Weight loss
- Nausea and vomiting
- Headache
- Muscle weakness, spasm and cramps
- Fatigue
- Restlessness and irritability
HYPOACTIVITY OF POSTERIOR PITUITARY
Cause
Diabetes Insipidus
Endocrine function of pancreas is performed by the
.
islets of Langerhans
Islets of Langerhans consist of four types of cells:
And functions
- A cells or α-cells, which secrete glucagon
- B cells or β-cells, which secrete insulin
- D cells or δ-cells, which secrete somatostatin
- F cells or PP cells, which secrete pancreatic
polypeptide
Insulin actions on carbohydrate
metabolism:
Increases transport and uptake of glucose by the cells
Promotes peripheral utilization of glucose
Promotes storage of glucose – glycogenesis
Inhibits glycogenolysis
Inhibits gluconeogenesis
Thus, insulin decreases the blood glucose level by:
i. Facilitating transport and uptake of glucose by
the cells
ii. Increasing the peripheral utilization of glucose
iii. Increasing the storage of glucose by converting
it into glycogen in liver and muscle
iv. Inhibiting glycogenolysis
v. Inhibiting gluconeogenesis
Function of insulin on protein
Insulin facilitates the synthesis and storage of proteins
and inhibits the cellular utilization of proteins by the
following actions:
Function of insulin on fat
Insulin stimulates the synthesis of fat. It also increases
the storage of fat in the adipose tissue
Normal blood glucose levels
And insulin release rate
80-100mg/dl
10
Insulin are produced @
Endoplasmic reticulum of Beta cells
AA does what to insulin
BS does what to insulin
Parasympathetic NS does what to insulin
Sympathetic NS does what to insulin
Antidibetic Hormone does what to insulin
Diabetic Hormone does what to insulin
Increase
Increase
Increase
Decrease
Decrease
Increase
What type of diabetes is not associated with obesity,but may be associated with acidosis or ketosis.
And which is reverse?
Type 1 is not associated with obesity,but may be associated with acidosis or ketosis.
But type 2 is associated with obesity,but may not be associated with acidosis or ketosis.
Symptoms of diabetes
Hypo secretion of insulin
Polyuria
Polydipsia
Polyhagia
Acidosis
Kussmaul breathing
Complications of diabetes
Neuropathy
Cataract
Hypertension
Retinopathy
Nephropathy
Hyper secretion of insulin results in
Hyper insulinism
What are the source of secretion of somatostantin
- Hypothalamus
- D cells (δ-cells) in islets of Langerhans of pancreas
- D cells in stomach and upper part of small intestine.
Functions of somatotastin
it inhibits the secretion of
both glucagon and insulin
2. It decreases the motility of stomach, duodenum and
gallbladder
3. It reduces the secretion of gastrointestinal hormones
gastrin, CCK, GIP and VIP
4. Hypothalamic somatostatin inhibits the secretion of GH
and TSH from anterior pituitary. That is why, it is also
called growth hormone-inhibitory hormone (GHIH)
Somatostatin brings out its actions through cAMP
Secretion of pancreatic somatostatin is stimulated
And stomach somatostatin is stimulated by?
by glucose, amino acids and CCK
Stomach chyme
Function of pp H from F cells
increase the secretion of
glucagon from α-cells in islets of Langerhans
PTH plays an important role in maintaining blood calcium
level. It also controls blood phosphate level.
Normal blood calcium level is
And it’s maintained by PTH by acting on
critical range of 9 to 11 mg/dL
1. Bones
2. Kidney
3. Gastrointestinal tract.
What reduces the amount of oxytocin receptors in the myometrium?
Decrease in oestrogen causes it
Antidiuretic hormone (ADH) is secreted mainly by _______ of hypothalamus. It is also secreted
by ___________ in small quantity
supraoptic nucleus
paraventricular nucleus
Oxytocin is secreted mainly by ______ of the hypothalamus. It is also secreted by ______ in small quantity
paraventricular nucleus
supraoptic
Nucleus
High oestrogen levels (in the absence of progesterone) has _____ feedback on LH and FSH secretion
positively feedback
Moderate oestrogen levels exert _____ feedback on LH and FSH secretion
negative feedback
Oestrogen in the presence of progesterone exerts ______ feedback on the HPG axis
negative
