pituitary gland disorders
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Pituitary Gland Disorders. Diabetes Insipidus (DI) is very different from the disease called sugar diabetes (diabetes mellitus) - PowerPoint PPT PresentationTRANSCRIPT
Pituitary Gland Disorders• Diabetes Insipidus (DI) is very different from
the disease called sugar diabetes (diabetes mellitus)– DI is caused by the insufficient release of ADH
from the neurohypophysis. Without ADH acting on the collecting ducts in the kidneys, the normal urine output of 1–1.5 liters per day increases to over 2.5 liters per day and dehydration and hypernatremia results
The Thyroid Gland• The butterfly-shaped thyroid gland is located
inferior to the larynx and anterior to the
trachea. It has two laterally placed lobes
separated by a bridge-like isthmus
The Thyroid Gland• Most of the thyroid gland is composed of
spherical groups of follicular cells called thyroid follicles– The follicles store
a 100-day supply of its two hormones in an inactivegel-like substance called TGB (forthyroglobulin)
• TGB is a large glycoprotein made
from the oxidation and iodination
of molecules of the amino acid.
tyrosine• The two hormones released
from TGB are:
–thyroxine or T4 (tetraiodothyronine)
–and T3 (triiodothyronine)
Thyroid Hormones
Thyroid Hormones In the blood, T3 and T4 are bound to pre-albumins, albumin,
and a specific carrier protein called thyroid-binding globulin (TBG)– Most T4 released from the thyroid is converted
“peripherally” (by enzymes in the blood) into T3 ,
which is a more active hormone • Together with hGH and insulin, thyroid
hormones accelerate body growth, particularly the growth of the nervous and skeletal systems
• Thyroid-stimulating hormone (TSH) is released by the anterior pituitary gland in response to TRH secreted into the portal system– The hypothalamus
responds to higher circulating levels of T3 and T4 via negative feedback to inhibitTRH secretion
Thyroid Hormones
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
HypothalamusTRH
Actions of Thyroid Hormones:
Increase basal metabolic rateStimulate synthesis of Na+/K+ ATPaseIncrease body temperature (calorigenic effect)Stimulate protein synthesisIncrease the use of glucose and fatty acids for ATP productionStimulate lipolysisEnhance some actions of catecholaminesRegulate development and growth of nervous tissue and bones
1
Anteriorpituitary
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rateStimulate synthesis of Na+/K+ ATPaseIncrease body temperature (calorigenic effect)Stimulate protein synthesisIncrease the use of glucose and fatty acids for ATP productionStimulate lipolysisEnhance some actions of catecholaminesRegulate development and growth of nervous tissue and bones
1
2
Anteriorpituitary
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rateStimulate synthesis of Na+/K+ ATPaseIncrease body temperature (calorigenic effect)Stimulate protein synthesisIncrease the use of glucose and fatty acids for ATP productionStimulate lipolysisEnhance some actions of catecholaminesRegulate development and growth of nervous tissue and bones
1
2
3
T3 and T4
released intoblood byfollicular cells
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rateStimulate synthesis of Na+/K+ ATPaseIncrease body temperature (calorigenic effect)Stimulate protein synthesisIncrease the use of glucose and fatty acids for ATP productionStimulate lipolysisEnhance some actions of catecholaminesRegulate development and growth of nervous tissue and bones
1
2
3
4 T3 and T4
released intoblood byfollicular cells
ElevatedT3inhibitsrelease ofTRH andTSH(negativefeedback)
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rateStimulate synthesis of Na+/K+ ATPaseIncrease body temperature (calorigenic effect)Stimulate protein synthesisIncrease the use of glucose and fatty acids for ATP productionStimulate lipolysisEnhance some actions of catecholaminesRegulate development and growth of nervous tissue and bones
1
2
3
5
4
Thyroid HormoneRegulation
• A goiter is an enlargement of the thyroid gland and may be associated with hyperthyroidism, hypothyroidism, or euthyroidism– In many third-word countries
dietary iodine intake is inadequate; the resultant low level of thyroid hormone in the blood stimulates secretion of TSH, which causes thyroid gland enlargement
Thyroid Hormones
The Parathyroid Glands• The parathyroid glands are small, round
masses of tissue attached to the posterior surface of the lateral lobes of the thyroid gland– There are usually two
parathyroid glands attached to each lobe of the thyroid, one superior and one inferior
Parathyroid Hormones• Calcitonin (Thyrocalcitonin) is made by the
parafollicular (C-cells) of the thyroid gland andwhen secreted lowers the blood calcium level
• An increase in blood calcium will stimulate the C-cells of the thyroid to secrete calcitonin – Increased calcitonin will cause a negative
feedback inhibition of parathyroid hormone (PTH) which
causes a decrease in blood calcium and an increase in blood phosphate levels
PARATHYROID HORMONES(Interactions Animation)
• Calcitonin
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• Parathyroid hormone (PTH) is made by the more numerous chief (principal) cells of the gland– PTH increases absorption
of Ca2+ from the GI tract and stimulates osteoclastic activity so that Ca2+ is released from bone into the blood
Parathyroid Hormones
PARATHYROID HORMONES(Interactions Animation)
• Parathyroid Hormone
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1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
2
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
3
2
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
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4 2
1
PTH also stimulatesthe kidneys to releaseCALCITRIOL.
High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
3
4 25
1
CALCITRIOL stimulatesincreased absorption ofCa2+ from foods, whichincreases blood Ca2+ level.
PTH also stimulatesthe kidneys to releaseCALCITRIOL.
High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
3
4 25
6
Calcium Regulation
The Adrenal Glands• There are two adrenal glands, one superior to
each kidney (also called the suprarenal
glands). During embryonic development, the
adrenal glands differentiate into two
structurally and functionally distinct regions• the adrenal cortex
• the adrenal medulla
Catecholamines like norepinephrine
Steroid hormones like cortisol
The Adrenal Glands
The Adrenal Cortex• The adrenal cortex is peripherally located and
makes up 80-90% of the total weight of the gland – The cortex is subdivided into three zones, each of
which secretes a different group of steroid hormones, all formed
from the cholesterol molecule
• Just deep to the CT capsule, the cells of the zona glomerulosa synthesize mineralocorticoid hormones
• The middle zone, or zona fasciculata, secrete mainly glucocorticoid hormones, primarily cortisol
• The inner zona reticularisis the site of synthesisof weak androgens (masculinizing hormones)
Adrenocortical Hormones
• Mineralocorticoids regulate the concentrations of Na+
and K+ in the blood (affects blood volume/pressure)– Aldosterone is the major hormone in this group
• Glucocorticoids influence glucose metabolism and the
ability to resists the effects of stress– Cortisol is the major hormone in this group
• Weak androgens (masculinizing sex hormones) have
little effect in men, but play an important role in
promoting libido in women
Adrenocortical Hormones
• The most important effects of aldosterone is
seen in the renin-angiotensin-aldosterone
system (RAAS)– The RAAS is stimulated by a decrease in blood
volume and/or blood pressure – as in cases of
dehydration or hemorrhage. Low BP stimulates
juxtaglomerular cells in the kidney to
secrete the
enzyme renin
RAAS
RAASRenin converts the plasma protein angiotensinogen
(produced in the liver) into angiotensin I. As
angiotensin I circulates to the lungs, an enzyme called
angiotensin converting enzyme (ACE) converts
angiotensin I to angiotensin II
– Angiotensin II stimulates the adrenal cortex to secrete
aldosterone (salt and H20 resorption indirectly increases
BP), and it is a
potent vasoconstrictor (which
directly increases BP)
RAAS
Glucocorticoids• Glucocorticoids (mainly cortisol) regulate
metabolism by promoting the breakdown of proteins and fats to form glucose (gluconeogenesis). Increased blood sugar levels assist the body to cope with stress– Their inflammatory effects result from inhibiting white
blood cells. Unfortunately they also retard tissue repair and slow wound healing • glucocorticoids are very useful in the treatment of chronic
inflammatory disorders such as Lupus, though long term side-effects are severe