MLB 203 BIOCHEMISTRY II
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HORMONES I
Lawrence Nugbienyo (PhD.) FACULTY OF APPLIED SCIENCES
lnugbienyo@atu.edu.gh
DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
pineal gland
What are hormones? pituitary gland
Hormones are organic parathyroid gland
substances, produced by
endocrine glands, secreted
thyroid
gland
into the blood stream to
adrenal
control metabolic and gland
pancreas
biological activities in target ovary
cells. testis
MLB 203 BIOCHEMISTRY II
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Classification of Hormones Pineal gland
Pituitary gland
Thyroid gland
Based on chemical nature:
❖ Peptide hormones – eg. antidiuretic hormone, Pancreas
Adrenal gland
glucagon, insulin, oxytocin.
Testis (male)
❖ Steroid hormones – eg. glucocorticoids,
mineralocorticoids, sex hormones. Ovary
(female)
❖ Amino acid derivatives – eg. epinephrine,
norepinephrine, thyroxine triiodothyronine.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Classification of Hormones
Based on Mechanism of Action:
❖ Group I hormones: bind to intracellular receptors; lipophilic; mostly
derivatives of cholesterol (eg. estrogens, androgens, glucocorticoids, calcitriol).
❖ Group II hormones: bind to cell surface (plasma membrane) receptors;
stimulate the release of second messengers. Group II hormones are
subdivided into three categories based on the chemical nature of the
second messengers.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Group I Hormones
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Group II Hormones
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Group II Hormones (cont.)
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Mechanism of Action of Group I
Plasma membrane
H H
(Steroid) Hormones H R
The hormone-receptor complex binds to specific regions on
the DNA called hormone responsive element (HRE), H R
Cytosol
causing increased expression of specific genes. Nucleus Acceptor
Gene
DNA Transcription
mRNA
mRNA
Translation
Specific protein
Biochemical
response
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Mechanism of Action of Hormone
Group II (A) Hormones
Receptor
GTP regulatory protein Plasma membrane
Adenylate
CAMP performs its role as a second messenger cyclase
Cytosol
ATP PPi
in eliciting biochemical responses.
Phosphodiesterase R C
AMP 4cAMP
( )
R C
R2C2
R
C C
R
R2(4 cAMP ) ATP ADP
Protein Phosphoprotein
MLB 203 BIOCHEMISTRY II
_____________ Phosphatase
Hormones I
Ultimate
Pi biochemical
9 FACULTY OF APPLIED SCIENCES response
DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Regulation
288
of TG Lipase BIOCHEMISTRY
ATP
Epinephrine
Norepinephrine
Glucagon, Thyroxine Adenylate cyclase
Glucocorticoids Hormone sensitive
TSH, ACTH, GH TG lipase b
(inactive)
Insulin, niacin, PGE1 ATP
Pi
cAMP Protein Phosphatase
kinase
Insulin
Phosphodiesterase
Caffeine ADP
Hormone sensitive
5 ’ AMP TG lipase a
(active)
Triacylglycerol Diacylglycerol
Free fatty acid FFA
Monoacylglycerol
FFA
Glycerol
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PGE1– Prostaglandin SCIENCES FFA–Free fatty acid).
E1; TG–Triacylglycerol; _____________
DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Mechanism of Action of
Group II (B) Hormones
Phosphatidylinositol 4,5-bisphosphate in
the plasma membrane is hydrolyzed by a
specific phospholipase C in response to
hormonal signals. Both products of
hydrolysis act as intracellular messengers.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
The Pituitary Gland
Hypothalamus
Hypothalamus is a specialized
center in the brain that functions as
a master coordinator of hormonal Anterior pituitary
(adenohypophysis)
action.
Pars intermedia
(intermediate lobe)
Posterior pituitary
(neurohypophysis)
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Hypothalamic Hormones
●
Thyrotropin-releasing hormone (TRH): consists of pyroglutamate, histidine and
proline. TRH stimulates anterior pituitary to release thyroid-stimulating hormone (TSH or
thyrotropin) which, in turn, stimulates the release of thyroid hormones (T3 and T4).
●
Corticotropin-releasing hormone (CRH): stimulates anterior pituitary to release
adrenocorticotropic hormone (ACTH) which in turn, acts on adrenal cortex to liberate
adrenocorticosteroids. CRH contains 41 amino acids.
●
Gonadotropin-releasing hormone (GnRH): a decapeptide. GnRH stimulates anterior
pituitary to release gonadotropins (luteinizing hormone (LH) and follicle stimulating
hormone (FSH).
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Hypothalamic Hormones (cont.)
●
Growth hormone-releasing hormone (GRH): consists of 44 amino acids. GRH
stimulates the release of growth hormone (GH or somatotropin) which promotes growth.
●
Growth hormone release-inhibiting hormone or somatostatin (GRIH): contains 14
amino acids. GRIH inhibits the release of growth hormone from the anterior pituitary.
●
Prolactin release-inhibiting hormone (PRIH): a dopamine and/or a small peptide that
inhibits the release of prolactin (PRL) from anterior pituitary.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Anterior Pituitary Hormones
Classification of Anterior Pituitary Hormones
I. Growth hormone-prolactin group.
II.Glycoprotein hormones.
III.Pro-opiomelanocortin family.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
Growth Hormone
Growth Hormone (GH): production is influenced by factors such as sleep,
stress (pain, cold, surgery), exercise, food intake, etc.
Maximum rate of production of GH occurs after the onset of sleep.
“If you don’t sleep, you won’t grow.”
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Biochemical Functions of Growth Hormone
1. Effects on growth
2. Effects on protein metabolism
3. Effects on carbohydrate metabolism
4. Effects on lipid metabolism
5. Effects on mineral metabolism
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Abnormalities of Growth Hormone Production
Dwarfism
Gigantism & Acromegaly
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Prolactin
lactogenic hormone, luteotropic hormone, mammotropin or luteotropin.
Primarily concerned with the initiation and maintenance of lactation.
Increases levels of several enzymes involved in carbohydrate and lipid
metabolism.
Promotes HMP shunt, increases lipid biosynthesis and stimulates lactose
production in mammary glands.
Promotes growth of corpus luteum and stimulates the production of
progesterone.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Glycoprotein Hormones
Thyroid stimulating hormone (TSH)
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH)
Human chorionic gonadotropin (hCG)
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Thyroid Stimulating Hormone (TSH)
Promotes the uptake of iodide from the circulation by thyroid gland.
Organification: conversion of iodide (I-) to active iodide (I+).
Proteolysis of thyroglobulin to release T3 and T4.
Increased synthesis of proteins, nucleic acids and phospholipids in thyroid
gland.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Follicle Stimulating Hormone (FSH)
In females: FSH stimulates
follicular growth, enhances the
production of estrogens.
In males: FSH stimulates
testosterone production, required
for spermatogenesis and growth
of seminiferous tubules.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Luteinizing Hormone (LH)
In females: stimulates the
In males: stimulates the production
production of progesterone from of testosterone from Leyding cells.
corpus luteum cells.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Human Chorionic Gonadotropin (hCG)
Produced by syncytiotrophoblast cells of placenta.
Levels of hCG in plasma and urine increase almost immediately after
implantation of fertilized ovum.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Pro-opiomelanocortin (POMC) Peptide Family
ACTH β -LPH (93 A.As)
1–39 42–134
α -MSH CLIP γ -LPH β -Endorphin (31 A.As)
1–13 18–39 42–101 104–134
β -MSH γ -Endorphin (15 A.As)
84–101 104–118
α -Endorphin (14 A.As)
104–117
Enkephalin
5
The members of the pro-opiomelanocortin (POMC) family
derived from POMC cleavage. (Numbers in blocks represent amino acids
in sequence; In the brackets are the number of amino acids–AAs;
(ACTH–Adrenocorticotropic hormone; LPH–Lipotropin;
MSH–Melanocyte-stimulating hormone; CLIP–Corticotropin like
intermediate lobe peptide).
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Adrenocorticotropic hormone (ACTH)
Promotes the conversion of ACTH Overproduction:
cholesterol to pregnenolone in the - causes Cushing’s syndrome:
adrenal cortex.
Hyper-pigmentation
Enhances RNA and protein synthesis
Negative nitrogen balance
and thus promotes adrenocortical
Impaired glucose tolerance
growth.
Hypertension
Increases lipolysis by activating
Edema
lipase of adipose tissue.
Muscle Atrophy
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
β Lipotropin Hormone (β-LPH)
Promotes lipolysis.
Increases mobilization of fatty acids.
Serves as a precursor for the formation of beta-
endorphins and enkephalins (natural analgesics).
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Melanocyte-stimulating hormone (MSH)
In some animals, MSH promotes synthesis of skin
pigment - melanin (melanogenesis).
In humans, MSH does not appear to play any role
in melanin synthesis.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Posterior Pituitary Hormones
Oxytocin Antidiuretic hormone (ADH)
Nipple stimulation, vaginal and
Stimulates kidneys to retain water.
uterine distention.
Diabetes insipidus (polyuria) – may
Induces labour. be caused by inadequate levels of
Milk ejection from breast. ADH or a defect in the receptors of
Inhibits synthesis of steroids. target cells.
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY
Hormones I
Summary of Hypothalamic and Pituitary Hormones
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DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
THANK YOU
MLB 203 BIOCHEMISTRY II
FACULTY OF APPLIED SCIENCES _____________
DEPARTMENT OF MEDICAL LABORATORY TECHNOLOGY Hormones I
