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