Download Hormonal Regulation of Growth, Development, and Metabolism

Hormonal Regulation of Growth,
Development, and Metabolism
Chapter 9.2
McGraw-Hill Ryerson
Biology 12 (2011)
METABOLISM
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Thyroid Gland is located in front of the trachea.
It produces hormones:
– Thyroxine (T4)
– Triiodothyronine (T3)
T4 and T3 regulate
– body metabolism and
– growth and differentiation
of
tissues
T4 and T3
• Tyrosine based hormones, dependent on iodine for
production.
• Lipophilic, travel through blood bound to a protein,
thyroxine binding globulin (TBG) and cross the cell
membrane easily to interact with nuclear receptors,
thyroid hormone receptor.
• T4 has a longer half-life than T3 and outnumbers T3 by
20:1 in the bloodstream, but T3 is 4 times as potent
(more active).
• Circulating T4 is converted to T3 by the removal of
iodine. T4 is considered a precursor to T3.
Effects of T4 and T3
• T4 and T3 help our body oxidize sugars and
nutrients (proteins, fats) at a faster rate.
– All the energy of glucose is transferred to heat and
ATP, (no storing of glucose) and ATP is consumed
during activity, therefore there is no weight gain.
• Also increase cardiac output, heart rate,
breathing rate, and production of RNA
polymerases (so increased protein synthesis –
as well as metabolism)
Metabolic rate
decreases
Hypothalamus
TRH inhibits
Pituitary
TSH
Thyroid
Thyroxine
Increase
metabolism
REGULATION of METABOLISM
REGULATION of METABOLISM
• Metabolic rate decreases
• hypothalamus sends thyroid releasing hormone (TRH) to
the anterior pituitary
• Anterior pituitary releases thyroid stimulating hormone
(TSH)
• TSH acts on thyroid to stimulate release of thyroxine.
• thyroxine raises metabolism by increasing sugar usage
by body tissues
• thyroxine levels feedback on hypothalamus and
pituitary to inhibit further release of TRH /TSH
Thryoid Disorders
• Hypothyroidism: low thyroid secretions
– glucose is not oxidized as quickly, and excess
glucose is converted to glycogen and stored.
– once glycogen stores are filled, excess sugar is
stored as fat.
http://www.holisticprimarycare.net/topics/topics-h-n/healthy-aging/94-the-clinical-picture-of-hypothyroidism
Thyroid Disorders: Goiter
Metabolic rate decreases
Goiter
• Lack of iodine for
producing T4 and T3
• TSH produced
continuously in effort to
increase levels of T4 and
T3
• NO Feedback because
functional T4 and T3 not
formed
• Overstimulated thyroid
enlarges
Hypothalamus
TRH
Pituitary
TSH
Thyroid
Other Hormones of the
Thyroid Gland
•
Thyroid Gland also produces calcitonin
–
Decrease calcium in blood by absorption from
blood to bones
http://ncwcbio101.wordpress.com/
• Parathyroid Glands (on the
thyroid) produce Parathyroid
hormone (PTH):
– increase Calcium in blood by
calcium release from bones, and
reabsorption at kidneys,
intestines)
– Also increases production of
active Vitamin D
• Normal blood levels of calcium are
important for proper functioning
of (for ex.) the nervous system and
blood clotting.
Other Metabolic Hormones
• In addition to TSH, the Pituitary Gland also
produces Growth hormone (somatotropin)
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Increase Protein synthesis, Breakdown of fats
Abnomal levels lead to: dwarfism, gigantism, acromegaly
Homework
• Pg 403 #4, 6, 8, 10, 11