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Copyright © 2006 by Elsevier, Inc.
Microscopic Appearance of the Thyroid Gland
Figure 76-1; Guyton & Hall
Copyright © 2006 by Elsevier, Inc.
Thyroid Hormone Synthesis & Secretion
Figure 76-2; Guyton & Hall
Copyright © 2006 by Elsevier, Inc.
Binding of Thyroid Hormones & Precursors to Thyroglobulin during Hormone Synthesis
OHO
I I
C
H NH2
COOHC
H H
I I
OHO
I I
C
H NH2
COOHC
H H
I
OHO
I I
C
H NH2
COOHC
H H
I
C
H NH2
COOHC
H H
HO
I
C
H NH2
COOHC
H H
HO
I
C
H NH2
COOHC
H H
I
HO
TyrosineTyrosine
3-Monoiodotyrosine (MIT)3-Monoiodotyrosine (MIT)
Thyroxine (TThyroxine (T44))
Th
yroglobu
lin M
olecule
Th
yroglobu
lin M
olecule3,3’,5’-Triiodothyronine (RT3)3,3’,5’-Triiodothyronine (RT3)
3,5-Diiodotyrosine (DIT)3,5-Diiodotyrosine (DIT)
3,5,3’-Triiodothyronine (T3)3,5,3’-Triiodothyronine (T3)
Copyright © 2006 by Elsevier, Inc.
Actions of Thyroid Hormones
Figure 76-5; Guyton & Hall
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Metabolic Effects of Thyroid Hormones
Parameter ↓ T3, T4 ↑ T3, T4
Basal metabolic rate ↓ ↑
Carbohydrate metabolism ↓ Gluconeogenesis ↑ Gluconeogenesis ↓ Glycogenolysis ↑ Glycogenolysis Normal serum [glucose] Normal serum [glucose] Protein metabolism ↓ Synthesis ↑ Synthesis ↓ Proteolysis ↑ Proteolysis Muscle wasting
Lipid metabolism ↓ Lipogenesis ↑ Lipogenesis ↓ Lipolysis ↑ Lipolysis ↑ Serum [cholesterol] ↓ Serum [cholesterol]
Thermogenesis ↓ ↑
Table 48-1, Boron & Boulpaep
Copyright © 2006 by Elsevier, Inc.
Hypothalamohypophyseal-Thyroid Axis
HypothalamusHypothalamus
ThyrotropeThyrotrope
ThyroidThyroid
TT33, T, T44
TRH TRH
TSHTSH
__
__
+
+
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Pathophysiology of Thyroid Hormones
• Graves’ disease – autoimmune disorder; immune complex mimics TSH – stimulates continual production of thyroid hormone – leads to hyperthyroidism and goiter formation.
• Cretinism – deficiency of thyroid hormones in childhood – results in severe growth retardation and mental retardation.
Copyright © 2006 by Elsevier, Inc.
Copyright © 2006 by Elsevier, Inc.
Hypothalamohypophyseal-Thyroid Axis in Graves’ Disease
HypothalamusHypothalamus
ThyrotropeThyrotrope
ThyroidThyroid
TT33, T, T44
TRHTRH
TSHTSH
__
+
__
+
TSI
+
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Histology of an Islet of Langerhans of the Pancreas
Figure 78-1; Guyton & Hall
Copyright © 2006 by Elsevier, Inc.
Metabolic Effects of Glucagon
StimulateInhibit
GlucoseFree fatty acidsKetoacidsAmino acids
Glucose
Aminoacids
Free fattyacids
LiverAdipose
tissue
Ketoacids
Glycogen
Glucose-P
Pyruvate
Plasma
Berne & Levy, Figure 47-19
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Approximate Rates of Insulin & Glucagon Secretion at Different Blood Glucose Levels
40 80 120 160 200 240
Plasma glucose (mg/dl)
100%
50%
0
100%
50%
0
Insu
lin R
esp
onse
(
)
Glu
cagon R
espon
se( )
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Anatomy of the Parathyroid Glands & Microscopic Appearance of Chief Cells
Figure 79-9;Guyton & Hall
Copyright © 2006 by Elsevier, Inc.
• Bone resorption ( osteoclasts) osteocytic osteolysis
• Kidney Ca2+ reabsorption phosphate reabsorption Na+ reabsorption (weak effect) 1,25-(OH)2-D3
• Intestine Ca2+ absorption phosphate absorption
PTH Actions
Copyright © 2006 by Elsevier, Inc.
06 8 10 12 14
50
100
PT
H s
ecre
tion
(%
max
imal
rat
e)
Total plasma [Ca2+] (mg/dL)
Plasma Calcium Concentration & PTH Secretion
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Hypocalcemia
DisorderPlasma [PTH]
Plasma [1,25-(OH)2-D3] UrineBone
Plasma [Ca2+]
Plasma [Phosphate]
Vitamin D deficiency
Chronic renal failure
(2°)
*
*
Phosphate
cAMP
Phosphate
( GFR)*Osteomalacia
Resorption
Resorption
* Primary events or disturbances
Surgical hypoparathyroidism
(2°) * Osteomalacia
Resorption cAMP
Phosphate
Castanzo, Table 9-17
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Primary Hyperparathyroidism
Plasma[PTH]
*
Plasma [1,25-(OH)2-D3] Urine
Phosphate
Ca2+
cAMP
Bone
Resorption
Plasma [Ca2+]
Plasma [Phosphate]
* Primary disturbance
Castanzo, Table 9-17
