BIOLOGY IISCI 4210
Ms Nurul Jannah
AhswiniSumithraKavita
KerkNeelashini Yeok Yoon
The Regulation of Hormone
Secretion by other Hormones
Introduction
Chemical messenger produced by endocrine glands.
Endocrine glands are stimulated by three main components of body
Nervous System
Releasing -Hormones
Regulation of Level of Specific
Substances in Blood
Releasing -Hormones
Hormone that stimulate the secretion of
other hormone.
4 main releasing-hormones
THYROTROPHIN RELEASING-HORMONES
CORTICOTROPHINRELEASING-HORMONES
GROWTH RELEASING-HORMONES
GORNADOTROPHINRELEASING HORMONES
CORTICOTROPHINRELEASING - HORMONES
• Also known as Corticotropin-releasing
factor (CRF) or Corticoliberin
• a peptide hormone and neurotransmitter
• found in most vertebrate tissues
• main function is the stimulation of the pituitary
synthesis of ACTH
• ACTH (Adrenocorticotropic hormone) modulates
the activity of the hypothalamic–pituitary–
adrenal axis during stress
• "Stressful" situations include
• Regulates important cardiovascular, metabolic,
immunologic, homeostatic functions including
water balance
• Abnormally high levels of CRH have been found
in the cerebrospinal fluid of people that have
committed suicide
Physical
• Trauma• Surgery• Exercise
Psychological
• Anxiety• Depression Physiological
• Hypoglecemia• Inflammation
• secreted by the paraventricular nucleus (PVN)
of the hypothalamus
• also synthesized in peripheral tissues, such as
T-lymphocytes , and is highly expressed in the
placenta
• In the placenta, CRH is a marker that
determines the length of gestation and the
timing of parturition and delivery
THYROTROPHINRELEASING - HORMONES
Also called thyrotropin-releasing factor (TRF).
Produced by the hypothalamus in medial neurons of the paraventricular nucleus.
It is a tropic, tripeptidal hormone that stimulates the release of Thyroid-stimulating hormone (TSH) and prolactin from the anterior pituitary.
• It travels across the median eminence to the anterior pituitary gland via the hypophyseal portal system.
• Then, stimulates the release of thyroid-stimulating hormone from cells called thyrotropes.
• Excess levels of TSH inhibit dopamine which will then stimulate the release of prolactin which in turn decreases Gonadotropin-releasing hormone (GnRH).
• TSH regulates follicular cells of the thyroid gland to produce Thyroid hormones (T4 and T3).
• T4 and T3 are crucial for metabolism rate regulation and which will affect the whole body cells metabolism and growth.
• Prolactin is to induce the expression milk (lactation).
• It also has several secondary effects including downgrading levels of testerone and estrogen, stimulate the formation of myelin, and many others.
The secretion of TRH which stimulating the secretion of TSH and other hormones in human.
GONADOTROPHINRELEASING - HORMONES
Gonadotropin-releasing
hormone (GnRH)
Luteinizing-hormone-releasing
hormone (LHRH)
Luliberin
Characteristics and Functions
• Trophicpeptide hormone.• Synthesized from hypothalamus.• The peptide belongs to
gonadotropin-releasing hormone family.
Characteristics
• Control the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from anterior pituitary.
Functions
Control of FSH and LH
• Releasing of FSH and LH are controlled by the size and frequency of GnRH pulses which by getting the feedback from androgens and estrogen.
Low frequency
• FSH is released.
High frequency
• LH is released.
Secretion of GnRH in Male & Female
Male
GnRH is secreted at a constant
frequency.
Female
Frequency impulses varies
during menstrual cycle.
A large amount of GnRH will be released just
before ovulation.
Importance of GnRH
• Pulsatile in all vertebrates
• Necessary for reproductive function.
• Controls a complex process of follicular growth, ovulation and corpus luteum maintenance in the female.
• For male, it controls the spermatogenesis.
GROWTHRELEASING - HORMONES
• known as growth-hormone-releasing factor (GRF, GHRF)
• Example: somatoliberin or somatocrinin
• 44[1]-amino acid peptide hormone
• produced in the arcuate nucleus of the hypothalamus
• appears in the human hypothalamus between 18 and 29 weeks of gestation
• It corresponds to the start of production of growth hormone and other somatotropes in fetuses
ORIGIN OF(GHRH)
• released from neurosecretory nerve terminals of the arcuate neurons
• carried by the hypothalamo-hypophyseal portal system to the anterior pituitary gland
• This will stimulates growth hormone (GH) secretion by stimulating the (GHRH) receptor
• released in a pulsatile manner• GHRH also promotes slow-wave sleep directly
Growth hormone is required for
normal postnatal growth bone growth
regulatory effects on protein, carbohydrate, and lipid
metabolism
Effect
GHRH stimulates GH production
Release; by binding to the GHRH
Receptor (GHRHR) on cells in the
anterior pituitary
Thank You