Transcript Hypothalamic and Pituitary Hormones

Hypothalamic Pituitary Hormones
Lecture NO : 2nd MBBS
Dr Muhammad Ramzan
Hypothalamic hormones - the definition
• These are the hormones/factors produced by the Hypothalamic
nuclei/neurons – the Neuro secretary cells
• Reach the anterior Pituitary through the portal veins to
stimulate/inhibit the release of hormones from it or
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• Travel along the axons of Neuro secretary cells to the posterior
pituitary for storage and released when required
2
Hypothalamic Hormones – 2 types
Releasing / Inhibitory and Neuro hormones
• Hypothalamic hormones are of 2 types
• Hypothalamic Releasing or Inhibitory hormones/factors for 1
the stimulation/inhibition of anterior pituitary gland
• Neuro hormones produced by the hypothalamic nuclei to be
stored in posterior pituitary for further release
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Hypothalamic pituitary hormones – 2 types
Hypothalamic Releasing (HRH) or
Hypothalamic Inhibitory hormones(HIH)
• These hormones are secreted by the Hypothalamic nuclei
• Transported to the Anterior Pituitary via Portal veins that
stimulate/inhibit to produce several hormones
• They are named as Releasing / Inhihibitory Hypothalamic
hormones for the respective Pituitary Hormones Like :
• Hypothalamic Stimulatory /Inhibitory hormone or factor for
Growth hormone (GHRH or GHIH)
Hypothalamic Releasing / inhibitory hormones/factor
Hypothalamic Neuro hormones
from PVN and Supraoptic nuclei
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These are synthesized in the hypothalamic nuclei - PVN SOP
Travel along the axons of secretary neurons to be stored in
posterior pituitary and are released directly into the :
Circulation in response to appropriate stimulus
These are the hormones of Posterior Pituitary/ Neuro hypophysis
Like Anti diuretic hormone/Vasopressin (ADH) and Oxytocin
Hypothalamus – the Neuro hormones
Neuro hormones – difference from Hypothalamic
Releasing/inhibitory hormones (3 points)
• Neuro hormones require no Hypothalamic releasing/Inhibitory
hormones (Requirement for synthesis)
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• Travel along the axons of hypothalamic secretary cells to the
Posterior Pituitary gland (method of transport )
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• Stored there as secretary vesicles and released into the
circulation in response to a stimulus (storage)
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Difference B/W Hypothalamic Stimulatory/Inhibitory hormones
and Hypothalamic Neuro hormones
Hypothalamic
Stimulator/Inhibitory
Hormones
Hypothalamic NeuroHormones
Requirement for
stimulation/inhibition
Require either of these for
their release/inhibition
Require no Hypothalamic
stimulatory/ inhibitory
Hormones
Transportation from
Hypothalamus to
Pituitary Gland
Are transported to Pit.
Gland Via Portal veins
Are transported via axons of
Neuro -secretary cells
Storage before their
release into circulation
Not stored in Pituitary
Gland, Are released
directly into systemic
Circulation
Stored in Axons of Neuro –
secretary cells, Released in
response to an approprpriate
stimulus
Parameters
Hypothalamic Releasing Hormones
– 5 (the major ones)
Hypothalamic Inhibitory Hormone HIH - 5
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Growth Hormone Releasing Hormone
- GHRH 1
Thyrotropin Releasing Hormone
- TRH
2
Corticotropin Releasing Hormone
- CRH
3
Gonadotropin Releasing hormone
- GnRH 4
Prolactin Releasing hormones
- PRH
5
(Others are Somatostatin and Dopamine , inhibit the Pit. Hor.)
Same is true for the existence of HIH with same names
Hypothalamic Releasing/Inhibiting Hormones 5
Pituitary Gland – the background
• Pituitary gland or Hypophysis is an endocrine gland, situated
below the hypothalamus
• It is enclosed in a bony cavity at the base of the skull called the
Sella Turcica (Turkish saddle)
• It is about the size of a pea and weighs 500- 900mg.
Turkish Saddle
Pituitary Gland – the Master gland
Receives messages from CNS
• Pituitary is also called as the Master gland, as it regulates the
secretions of many glands and influences the :
• Body growth, reproductive system and metabolism
• Pituitary Is a link B/W the hypothalamus and endocrine
system and receives messages (HRH and HIH) from CNS
• Thus establishing the science of Neuro endocrinology
Pituitary Gland – the divisions
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Pituitary gland is divided into 2 :
Anterior Pituitary gland or Adenohypophysis
Posterior Pituitary gland or Neuro hypophysis
Pituitary Gland – the division
Hormones of Anterior Pituitary Gland 1
6 in no
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Are 6 in Number
Growth Hormone or GH
Thyroid Stimulating Hormone or/ Thyrotropin - TSH
Adrenocorticotropic hormone /Corticotrophin – ACTH
Prolactin or PRL
Hormones of Anterior Pituitary gland – the others
the Gonadotropins
5 Luteinizing Hormone or LH
6 Follicular Stimulating Hormone or FSH
No 5 and 6 are called collectively as Gonadotropins
Melanocyte Stimulating hormone is secreted from the middle
part of the Pituitary gland
Anterior Pituitary Hormones
Types of Anterior Pituitary hormones
Tropics and non tropics
• Hormones from the Anterior Pituitary gland are divided into
2 on the basis of regulating the :
• Growth/nutrition/functions of other endocrine glands in the
body
• Tropics and
• Non Tropics
Anterior pituitary hormones - the Tropics - 4
• Four (4) of these ones are called Tropic Hormones as they
stimulate the growth, nutrition and function of :
• other endocrine glands
• TSH : regulates Thyroid gland secretion
• ACTH : controls secretion of Adrenal Cortex
• FSH : maintains female sex hormones level and follicle growth
• LH : regulates Testosterone and secondary sex characters
The Tropic hormones – 4 in no
Hormones of anterior Pituitary
the Non Tropics. 2 in no
• Rest 2 of the anterior Pituitary hormones are the ones that do not
stimulate the secretion of other endocrine glands
• Growth hormone : Promotes protein synthesis and cell division in
cartilage; bone, muscles and organs
• Prolactin : promotes development of breast and milk production
after child birth
• Melanocyte Stimulating Hormone : regulates skin colour changes
and degree of pigmentation in Melanocytes
Hormones of Posterior Pituitary gland - 2
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The Posterior Pituitary produces 2 hormones :
Vasopressin /Ant diuretic hormone (ADH) and Oxytocin.
ADH : maintains water; fluid /electrolyte balance. And BP
1
Oxytocin : stimulates the contraction of the smooth muscles of
the uterus; Myoepithelial cells of ducts of mammary glands
and vas deferens
2
Posterior Pituitary hormones – the actions