Neural-Endocrine System Flashcards by Lauren Horsburgh

What part of the pituitary connects the hypothalamus to the pituitary?

Infundibulum

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What is the name of the capillary system which exists between the anterior pituitary and hypothalamus?

Hypothalamohypophyseal portal system

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What type of connection exists between the posterior pituitary and the hypothalamus?

Neural connection

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Neurons from which two parts of the hypothalamus interact with the pituitary gland?

Paraventricular nucleus

Supraoptic nucleus

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What is the name of the junction between the infundibulum and hypothalamus?

Median eminence

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Within a depressed region in which bone does the pituitary gland sit?

Sphenoid bone

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Which hormones are secreted by the posterior pituitary?

ADH

Oxytocin

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Which hormones are secreted by the anterior pituitary?

Growth hormone
Lutenizing hormone
Follicle stimulating hormone
Adrenocorticotrophic hormone
Thyroid stimulating hormone
Prolactin

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The hormones secreted by the posterior pituitary are produced in the hypothalamus. T/F?

True

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What is the function of the hypothalamus?

Controls body temperature, hunger, thirst, fatigue, sleep

Secretes neurohormones which stimulate the release of hormones from the pituitary gland

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What regulates the secretion of follicle stimulating hormone and lutenizing hormone?

Gonadotrophin releasing hormone from the hypothalamus

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What hormones control the release of growth hormone?

Growth hormone releasing hormone

Growth hormone inhibitory hormone (somatostatin)

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The inhibitory effect of which molecule regulates the secretion of prolactin?

Dopamine

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What is the action of growth hormone?

Stimulates insulin like growth factor production in the liver. This stimulates amino acid uptake and thus DNA synthesis and mitosis in cells. Growth hormone also increases gluconeogenesis, promotes fat breakdown in adipose tissue and decreases glucose uptake by cells to promote non-carbohydrate sources of energy

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What event does lutenizing hormone stimulate in women?

ovulation

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What is the role of follicle stimulating hormone in women?

Stimulates the growth and development of follicles during the first half of each menstrual cycle
Needed for oestrogen secretion by the developing follicle

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What is the role of follicle stimulating hormone in men?

Required for spermatogenesis by sertoli cells

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What is the role pf lutenising hormone in men?

Stimulates testosterone secretion by leydig cells

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What important structure exists directly above the pituitary gland?

Optic chasm

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What cells in the anterior pituitary secrete growth hormone?

Somatotrophs

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What percentage of the anterior pituitary is made up of somatotrophs?

50%

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What cells in the anterior pituitary secrete LH and FSH?

Gonadotrophs

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What percentage of the anterior pituitary is made up of gonadotrophs?

10%

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What cells in the anterior pituitary secrete ACTH?

Corticotrophs

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What percentage of the anterior pituitary is made up of corticotrophs?

10-15%

What cells in the anterior pituitary secrete TSH?

Thyrotrophs

What percentage of the anterior pituitary is made up of thyrotrophs?

What cells in the anterior pituitary secrete prolactin?

Lactotrophs

What percentage of the anterior pituitary is made up of lactotrophs?

20%

At what time of day is growth hormone mainly secreted?

At night

Growth hormone stimulates the production and release of IGF-1 from the liver. IGF-1 can act to propagate the action of growth hormone in which tissues?

Bone Adipose tissue Metabolism

What is the importance of oxytocin?

Important in labour - stimulates cervical dilatation and uterine contractions important in breast feeding - stimulates let down reflex

Describe the process by which ADH works on the collecting ducts to increase water reabsorption in the kidney?

ADH binds to V2 ADH receptor on the basolateral membrane of the kidney collecting ducts which stimulates a GPCR that activates adenylyl cycle;ase causing production of cAMP and PKA. This increases the exocytosis of the aquaporin water channel containing vesicles (AVPR2) and inhibits the endocytosis of these vesicles in order to increase aquaporin 2 channel formation and insertion in the apical membrane

Define diabetes insipidus

Passage of large volume (>3L) of dilute urine which results in polyuria, polydipsia and nocturne in the absence of hyperglycaemia and hypercalcaemia

What are the possible causes of cranial diabetes insipidus?

``` Idiopathic Genetic Trauma Tumours Infections Inflammatory conditions of the posterior pituitary ```

What are the possible causes of nephrogenic diabetes insipidus?

Resistance to ADH Genetic AVPR2 mutation Secondary to nephrogenic damage Secondary to drug use, metabolic upset or renal disease

How is diabetes insipidus tested for?

A water deprivation test

Describe the water deprivation test for diabetes insipidus

Patients are deprived of fluid for 8 hours and their plasma and urine osmolality is monitored A synthetic ADH (ddAVP) is then given and the urine osmolality is reassessed If the problem is cranial then urine osmolality is increased by ddAVP, if the problem is nephrogenic then urine osmolality is unaffected by ddAVP

What is the most common secretory pituitary adenoma?

Prolactinoma

How common are secretory ACTH tumours?

20% of pituitary adenomas

How common are secretory GH tumours?

15% of pituitary adenomas

How common are secretory TSHomas?

<1% of pituitary adenomas

Pituitary adenomas are often asymptomatic. T/F?

True

If an incidental pituitary adenoma is found, what factors are important to check?

Check for hormone excess Check for hypopituitarism Check that the tumour has had no effects on the visual fields

What are the clinical features of a prolactinoma?

Galactorrhoea Menstrual disturbance and sub fertility in women Reduced libido or erectile dysfunction in men

How are prolactinomas managed?

Dopamine agonists such as cabergoline | Surgery if the tumour is large or affects visual fields

What is acromegaly?

The excessive production of GH (and resultant excessive production of IGF-1) in adults usually caused by a pituitary adenoma

What are the symptoms of acromegaly?

``` Sweating headaches tiredness increase in ring or shoe size joint pains ```

What are the clinical signs of acromegaly?

Coarse facial appearance Enlarged tongue Enlarged hands and feet visual field loss

What complications may result from acromegaly?

Hypertension diabetes / impaired glucose tolerance increased risk of bowel cancer heart failure

What tests can be used to diagnose acromegaly?

Glucose tolerance tests - glucose load fails to suppress GH and test may also reveal underlying diabetes IGF-1 levels MRI of the pituitary

How is acromegaly managed?

Transsphenoidal route surgery (often not curative) somatostatin analogues to inhibit GH secretions Pituitary radiotherapy

What are the risks associated with the use of radiotherapy in the treatment of acromegaly?

Hypopituitarism | Long term problems

What is hypopituitarism?

Failure of anterior pituitary function

What is the name for failure of anterior pituitary function which affects all hormone axes?

Panhypopituitarism

How is hypopituitarism managed?

Hormone replacement

If all hormonal axes are affected by hypopituitarism, which hormone is given first?

Cortisol

What factors can cause hypopituitarism?

``` tumours radiotherapy infarction infiltrations trauma congenital disorders ```

Hypogonadoptrophic hypogonadism can be cause by hyperprolactinaemia as a result of any drug which interferes with dopamine action. This includes...?

``` Antipsychotics Antiemetics (metoclopramide, domperidone) Antidepressants (SSRIs, MOA-1, TCA) Opiates H2 receptor antagonists ```

Dopamine agonists can be used to treat prolactinomas. Give examples of these drugs.

Cabergoline Quiagolide Bromocriptine

Cabergoline is a oral dopamine agonist used in the treatment of prolactinomas. What are the risks associated with this drug?

Cardiac fibrosis | Valvopathy

What type of receptors does ADH bind to in vascular smooth muscle to cause vasoconstriction?

V1 receptors

What is desmopressin and when may it be used?

A synthetic analogue of ADH which is used for maintenance therapy in cranial diabetes insipidus or acute therapy

What drug is the mainstay of treatment for hypothyroidism?

Levothyroxine

Carbimazole and propulthiouracil (PTU) can be used to treat hyperthyroidism. Why is carbimazole the preferred treatment?

Carbimazole is the more potent drug

How do thianamides such as carbimazole and Propylthiouracil work to treat hyperthyroidism?

They inhibit idodide oxidation, iodination of tyrosine and coupling of iodotyrosines to reduce thyroid hormone synthesis

In addition to its ability to reduce thyroid hormone synthesis, what other effects does Propylthiouracil exhibit to treat hyperthyroidism?

Inhibits peripheral conversion of T4 to T3

In addition to the use of thionamides in the treatment of hyperthyroidism, what drugs can be used in symptom management?

Beta blockers or calcium channel blockers

What medications may be used pre-operatively in patients with hyperthyroidism?

Potassium iodide

Glucocorticoids are protein-bound steroid hormone which have many systemic effects. These include...?

Anti-inflammatory by inhibiting transcription of genes for pro-inflammatory cytokines Reduced T lymphocytes Counter regulatory metabolic effects - gluconeogenesis, increased adiposity improved alertness mineralocorticoid effect

What preparation of glucocorticoids is closest to physiological cortisol?

Hydrocortisone

Glucocorticoids are commonly prescribed drugs. How might they be administered?

``` Topically Nasally Inhaled Orally Subcutaneously IM IV ```

Fludrocortisone is an oral mineralocorticoid used in the treatment of which diseases?

Addison's disease | Postural hypotension

Spironolactone is a competitive antagonist of mineralocorticoid, androgen and progesterone receptors. Thus, the use of this drugs as a mineralocorticoid receptor blocker can have the unwanted side effects of...?

Gynaecomastia | Hyperkalaemia

Eplerenone is a selective mineralocorticoid antagonist. When might it be used clinically?

In the treatment of primary aldosteronism, heart failure and hypertension

Bisphosphonates are used in the treatment of osteoporosis, Paget's disease and metastatic bone disease to reduce bone resorption. Give examples of these drugs?

Alendronate, Pamidronate, zolendronate | risedronate

What is the mechanism of action of denosumab in the the treatment of osteoporosis?

Monoclonal antibody inhibits RANKL to reduce resorption

Teriparatide is a drug which increases bone formation. This is a recombinant for of which endogenous hormone?

PTH

How can the use of glucocorticoids affect bone density?

Decrease bone density by decreasing calcium absorption and increasing PTH leading to increased bone resorption and decreased bone formation