lecture 6 endocrineii

8/9/2019 Lecture 6 EndocrineII

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Lecture 6

2. The Important Endocrine Glands and Their Hormones

A. The pituitary hormones

anatomy of the pituitary gland and its relation to the

hypothalamus

anterior lobe

intermediate lobe

posterior lobe

pituitary stalk

supraoptic neucleus

paraventricular nucleus

hypothalamus-pituitary portal system

short portal system



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Regulation of pituitary hormone secretion by the

hypothalamus

secretion of posterior pituitary hormones: a typicalneuroendocrine regulatory mechanism

secretion of anterior pituitary hormones: a typical

endocrine regulatory mechanism

important releasing/inhibiting hormones produced

in hypothalamus:

- Corticotropin-releasing hormone (CRH)

- Thyrotropin-releasing hormone (TRH)

- Gonadotropin-releasing hormone (GnRH)

- Growth-hormone-releasing hormone (GHRH)

- Prolactin-releasing hormone (PRH)

- Prolactin-inhibitory hormone (PIH)



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Posterior pituitary hormones

Antidiuretic hormone ( ADH, vasppressin)

- chemistry: 9 amino acid peptide, produced

primarily by supraoptic nucleus and small

amount by paraventricular nucleus

- actions:

1) water retention by the kidney

qurine volume and o ECF

2) vasoconstriction (in large amounts)

- regulation/stimuli:

1) blood (or ECF) osmolality/osmoreceptors

2) blood volume



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3) others: alcohol, nicotine, barbiturates, etc.

- abnormality: diabetes insipidus Oxytocin

- chemistry: 9 amino acid peptide, produced

primarily by paraventricular nucleus and small

amount by supraoptic nucleus

- actions: 1) regulating breast milk release

2) contraction of pregnant uterus


suckling by a nursing infant

crying sounds from a baby

fear and stress inhibit release



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anterior pituitary hormones

Growth hormone

Prolactin

Thyroid-stimulating hormone

Adrenocorticotrophic hormone

Folicle-stimulating hormone

Luteinizing hormone

Growth hormone (GH)

- chemistry:191 peptide

- actions: see Fig.13-7


Growth hormone releasing hormone (GHRH)



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Growth hormone inhibitory hormone

(somatostadin)

other stimuli:

deep sleep

low blood glucose

stress

amino acids (arginine)

- abnormality:

dwarfism

gigantism (acromegaly)



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B. The Thyroid Hormones

The main hormones secreted by the thyroid gland are

iodinated derivatives of thyroxine (T4) andtriiodothyronine (T3).

Synthesis and secretion of thyroid hormones



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Regulation of thyroid synthesis

and secretion - hypothalamic-pituitary-thyroid axis

Hypothalamus TRH

anterior pituitary TSH

thyroid T3 & T4 negativefeedback on the hypothalamus

and the anterior pituitary



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Thyroid hormone transport and metabolism - T3 and

T4 are carried by thyroxine-binding globulin and

albumin

Effects of thyroid hormones on metabolic processes

Metabolic rate: increased BMR

Calorogenic: increased heat production (oxidative

metabolism)

Sympathomimetic: Fight or Flight

Cardiovascular: increased heart rate and

contractions Growth: essential for normal growth of skeletal

system (permissive or synergistic with GH, insulin-

like growth factors), CNS, ANS

Nervous system: development and maturation



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Myxedema causing

puffiness of the face inan adult with

hypothyroidism.

Disorders of thyroid function

Hypothyroidism

- Myxedema - Hypothyroidism occurring in

adulthood. Clinical features include lethargy, cold

intolerance, decreased sweating, bradycardia,

tongue enlargement, and non-pitting edema of

the skin due to infiltration of the subcutaneoustissues by metachromatic proteoglycans.



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- cretinism: A type of mental retardation and

bodily malformation caused by severe,uncorrected thyroid deficiency in infancy and

early childhood.

Hyperthroidism

- Grave¶s disease: Grave¶s disease is an

autoimmune disease in which the immune

system produces antibodies which stimulate

the TSH receptors of the thyroid gland,

resulting in overproduction of thyroidhormones. Symptoms: increased pulse rate,

increased sweating, heat intolerance, hair

loss, inflammation of the eyes, swelling of

the tissues around the eyes, and protrusion

of the eyes.



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- Goiter: an enlargement of the thyroid gland,

often resulting from the deficiency of iodine inthe diet (simple goiter) or other causes of

hyperthytoidism



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C. The Adrenal Glands

Adrenal medulla

Adrenal cortex

Three specific zones and each produces a specificclass of steroid hormone

Zona glomerulosa - mineralocorticoids

Zona fasciculata - glucocorticoidsZona reticularis - androgens



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glucocorticoids (cortisol)

- regulation of glucocorticoid secretion



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- physiological effects of glucocorticoids:

liver: increases gluconeogenesis

increases glycogen synthesis

skeletal muscle:

dcreases protein synthesisincreases protein degradation

decreases glucose uptake

adipose tissue:decreases glucose uptake

increases lipid mobilization

the permissive actions



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effects on blood vessels and blood cells:

enhances responsiveness of blood vessels

increases neutrophils, RBC and plateletesdecreases eosinophils and basophils

- pharmacological effects of glucocorticoids

anti-inflammatory effects

immunosuppressive effects

mineralocorticoids (aldosterone)

- regulation of mineralocorticoid secretion

- effects of mineralocorticoids:o ECF o blood volume o BP & CO

increases excretion of potassium

retains more sodium



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abnormalities of adrenal cortex function

excess secretion of glucocorticoids

- Cushing¶s syndrome:

redistribution of fat

Hypertention

increased susceptibility to infection

osteoporosis

adrenal insufficiency

- Addison¶s disease:

low plasma Na+, high plasma K+low blood pressure

muscle weakness

vomiting, dehydration

low blood sugar

excess pigmentation of skin



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D. The Endocrine Pancreas

Islets of Langerhans

Insulin

synthesis andsecretion of insulin

- a double-chain

peptide hormone

with 51 aa- beta cells

- derived from

proinsulin, a large

precursor



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regulation of its synthesis and secretion

- stimulators:

increased blood glucose

amino acids

fatty acids

glucose-dependent insulinotropic peptide (GIP)

acetylcholine (parasympathetic activity)glucagon-like peptide 1 (GLP-1)

- inhibitors:

somatostatin

epinephrine

norepinephrine



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metabolic effects of insulin

- carbohydrate metabolism

- lipid metabolism

- protein metabolism



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Glucagon

synthesis and secretion of glucagon

- a single-chain peptide hormone with 29 aa alpha

cells

- derived from proglucagon, a large precursor

regulation of its synthesis and secretion

- stimulators:

low blood glucose

amino acidsacetylcholine

epinephrine

norepinephrine



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- inhibitors:

fatty acidsSomatostatin

insulin

metabolic effects of glucagon (opposite to insulin)

- carbohydrate metabolism

- lipid metabolism

- protein metabolism



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Metabolic regulation by pancreatic hormones: the fed

state vs the fasted states

Fed state Fasted state



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Diabetes Mellitus

Type I, insulin-dependent diabetes mellitus

- Insulin deficiency

- More during adolescence

- Auto-immune disease

Type II, non-insulin-dependent diabetes mellitus

- Lake of insulin response at the target tissues

(insulin resistance)

- More in obese people but obese is not the cause

- Strong genetic component



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lecture 6 endocrineii

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