Chapter3 The Hypothalamus and Pituitary Part I

The Hypothalamus and Posterior Pituitary

Reference - Textbook

Reference – Course Website

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Content

• Introduction• Oxytocin• Vasopressin

INTRODUCTION

Anatomical and Functional Connection Between the Hypothala

mus and Pituitary

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• hypophyseal portal system

• Hypothalamo hypophyseal tract

Case: Mr. Jones, a 30-year-old man

• 6 weeks earlier– began passing a lot of urine

• Once or twice per hour• Full bladder four or five times during the night

– Unusually thirsty• Constantly drinking water• Urine was very pale

• in recent weeks– Headaches at night or waking– Forgetful– Erection dysfunction

Case: Mr. Jones, a 30-year-old man• Test at GP (General Physician)

– Urine test• No protein, no glucose

– Blood test• Glucose and calcium level normal

• Test at endocrine clinic– Looked uncomfortable– Dehydrated with a dry mouth and tongue– Body Temperature normal– Resting pulse rate: 100 b.p.m.– Blood pressure: 105/65 mmHg– Fundoscopy: optic nerve to be swollen in both eyes– Visual field test:

• loss of vision in both temporal (outer) halves of the field– Memory problem:

• Confuse and could not remember how he had got to the hospital or what he eaten that day

• Knew the name of his girlfriend and could remember distant events

Visual Field Defect

Oxytocin and VasopressinThe Hormone of the Posterior

Pituitary• Small peptides – nine amino peptide

– Seven of them are common

• Synthesized in the hypothalamus by magnocellular neurons

• Action potential initial release in the nerve

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Synthesis and Release of Vasopressin and Oxytocin

OXYTOCIN

Role of Oxytocin (OXT)

• Effect on mammary glands. – Cause the contraction of the myoepithelial cells ---

milk ejection

– Unconditioned and conditioned reflex

• Effect on uterus– stimulate the smooth muscle contraction, especially

that towards the end of gestation.

– at least partially responsible for causing birth of the baby

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OXYTOCIN

Oxytocin Release: Neuroendocrine Reflex

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Clinical Use

• Oxytocin– Induce labor– Increase uterine contractions during labor– Reduce postpartum bleeding after labor

• Atosiban: the antagonist of oxytocin receptor– Treatment of the preterm labor

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Recent Work about Oxytocin

OxytocinBehavior Hormone

Cardiovascular Hormone

Gastrointestinal Hormone?

VASOPRESSIN (ADH)

Roles of ADH

• Antidiuretic effect

• Pressure effect

– constricting the arterioles everywhere

• Neurotransmitter

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Vasopressin ReceptorsVasopressin ReceptorsV2-receptor:

collecting ductVascular endothelial cells

V1(a)-receptor: vascular smooth muscle

V3(1b) receptor: neurons (in CNS and ENS)Corticotropin cells (in pituitary gland)

Disorders of Vasopressin

• Deficiency– Caused by a tumour or trauma of the brain– Diabetes inspidus (hypothalamic or cranial)– Polyuria – large volumes of very dilute urine– Polydipsia (烦渴） - excessive thirst– Treatment:

• Desmopressin – a synthetic analogue of vasopressin

Disorders of Vasopressin

• Excess– Causes:

• Neoplasm-Lung cancer• Neurological disease – meningitis (脑膜炎）• Lung disease – pneumonia and tuberculosis• Prescribed drug – carbamazepine （立痛定）

– Syndrome of inappropriate ADH (SIADH)• Urine more concentrated • Hyponatraemia

– Headache, nausea, vomiting, confusion, coma

Clinical Use of Vasopressin

• To teat the diabetes insipidus• Reduce bleeding during gastrointestinal

surgery• Boost factor VIII concentration in mild

haemophilia

Explanation of Mr. Jones’ Syndromes and Signs

• 6 weeks earlier– began passing a lot of urine– Unusually thirsty

• in recent weeks– Headaches at night or waking– Forgetful– Erection dysfunction

Explanation of Mr. Jones’ Syndromes and Signs

• Test at endocrine clinic– Looked uncomfortable– Dehydrated with a dry mouth and tongue– Body Temperature normal– Resting pulse rate: 100 b.p.m.– Blood pressure: 105/65 mmHg– Fundoscopy: optic nerve to be swollen in both

eyes– Visual field test: loss of vision in both temporal

(outer) halves of the field– Memory problem