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