The Pituitary Glands And Its Disorders Flashcards
The pituitary gland has a dual blood supply.
What are these supplies?
the first is via the long and short pituitary arteries
- the second is from the hypophyseal portal circulation (this begins as a capillary plexus around the Arc)
What 6 hormones are released from the anterior pituitary, and what is their role?
- Adrenocorticotrophic hormone (ACTH): regulation of adrenal cortex
- Thyroid-stimulating hormone (TSH): thyroid hormone regulation
- Growth hormone (GH): growth
- Luteinising hormone (LH): reproductive control
- Follicle-stimulating hormone (FSH): reproductive control
- Prolactin (PRL): breast milk production
What 2 hormones are released from the posterior pituitary, and what is their role?
Anti-diuretic hormone (ADH): constantly regulates and balances the amount of water in your blood
Oxytocin: myocytes around the breast that contract to let milk out are under the control of oxytocin; oxytocin also makes the uterus contract when you’re having a baby
What are some different types of pituitary tumours?
HORMONE HYPERSECRETION
SPACE-OCCUPYING LESION:
- headaches
- visual loss (field defect)
- cavernous sinus invasion
HORMONE DEFICIENCY STATES:
- interfere with the surrounding normal pituitary
Tumours of the anterior pituitary can cause syndromes of hormone excess.
List the syndrome associated with the overexpression of each hormone from the anterior pituitary.
GH: Acromegaly
ACTH: Cushing’s Disease
TSH: Secondary thyrotoxicosis
LH/FSH: (non-functioning pituitary tumour)
PRL: Prolactinoma
Describe the control of growth hormone.
It has a stimulatory hormone (GHSH) and an inhibitory hormone (somatostatin). The interplay between these two means that GH is released in pulses.
GH acts on the liver to produce certain growth factors. One of these is IGF-1, which causes long bone growth for linear growth.
The negative feedback is mainly supplied by the IGF-1.
When we have a pituitary tumour producing too much GH, this will affect our growth and our metabolism.
What are some systemic effects of GH/ IGF-1 excess (+ some other consequences)?
- acral enlargement: rings too small, spade-like hands, increased shoe size, carpal tunnel syndrome
- increased skin thickness
- increased sweating
- skin tags and acanthosis nigricans
- changes in appearance: inter-dental spacing
- visceral enlargement
- metabolic changes
- impaired fasting glucose
- impaired glucose tolerance
- diabetes mellitus
- insulin resistance
- reduced total cholesterol
- increased triglycerides
- increased nitrogen retention
Some other consequences include:
- cardiomyopathy (diseases of the heart muscle)
- hypertension
- bowel polyps (small growths)
- colonic cancer
- multinodular goiter
- hypogonadism
- arthropathy (disease of a joint)
- OSA (obstructive sleep apnoea)
List some actions of cortisol.
It increases plasma glucose levels:
increased gluconeogenesis
decreased glucose utilisation
increased glycogen storage
It increases lipolysis:
- provides energy
Proteins are catabolised:
- releases amino acids
Na+ and H2O are retained:
- maintains BP
It has anti-inflammatory effects.
It causes increased gastric acid production.
What happens as a result of Cushing’s Syndrome?
CHANGES IN PROTEIN AND FAT METABOLISM:
change in body shape
central obesity
moon face
buffalo hump
thin skin, easy bruising
osteoporosis (brittle bones)
diabetes
CHANGES IN SEX HORMONES:
excess hair growth
irregular periods
problems conceiving
impotence
SALT AND WATER RETENTION:
high blood pressure
fluid retention
List some drugs that interfere with dopamine and prolactin secretion.
antiemetics (effective against vomiting and nausea)
antipsychotics
oral contraceptives/ hormone replacement therapy
What are some features of prolactin excess (hypogonadism)?
infertility
oligoamenorrhoea (irregular menstrual periods)
amenorrhoea (no menstrual periods)
galactorrhoea (milky discharge from breasts)
reduced libido
impotence
What is the treatment for prolactinomas?
Dopamine agonists (such as bromocriptine and cabergoline), not surgery.
Describe non-functioning pituitary tumours.
they make up 30% of all pituitary tumours
no syndrome or hormone excess is produced
can cause symptoms due to space occupation (headaches, nerve palsies, visual field defects)
the treatment would be surgery, as there is no effective medical therapy
What are possible treatments for pituitary adenomas?
SURGERY:
transsphenoidal (through nose and sphenoid bone)
adrenalectomy
RADIOTHERAPY (slow)
DRUGS:
block hormone production
stop hormone release
List some causes of pituitary failure.
tumour
trauma
infection
inflammation (sarcoidosis [the abnormal collection of inflammatory cells], histiocytosis [excessive number of tissue macrophages])
iatrogenic (illness caused by medical examination/ treatment)
What are the effects of hypopituitarism?
It affects the thyroid:
bradycardia
weight gain
cold intolerance
hypothermia
constipation
It affects sex steroids:
oligomenorrhoea
reduced libido
hot flushes
reduced body hair
It reduces cortisol:
tiredness
weakness
anorexia
postural hypotension
myalgia (pain in a muscle)
It reduces GH:
tired
central weight gain
What would be the treatment for hypopituitarism?
For the thyroid effects, we would give thyroxine.
For the sex steroid effects, we would give testosterone and oestrogen.
For the reduced cortisol, we would give hydrocortisone.
For the reduced GH, we would give GH.
What does vasopressin control, and what are its actions?
CONTROL:
increased plasma osmolality
decreased BP (baroreceptors)
decreased PaO2, increased PaCO2 (cortisol, sex steroids, angiotensin II)
ACTION:
collecting ducts, to increase permeability for H2O for the reabsorption of free water
vasoconstriction
Describe the Syndrome of Inappropriate ADH (SIADH), and how you would diagnose and treat it.
It is when the body has too much ADH. This could be caused by a brain injury/ tumour, lung cancer or infection, asthma, or have a metabolic cause such as hypothyroidism or Addison’s.
We diagnose it by checking bodily fluids:
if there is low plasma Na+
if there is low plasma osmolality
if there is high urine osmolality
if there is high urine sodium
Treatment would involve fluid restrictrion.
Describe Diabetes Insipidus, and how you would diagnose it.
It is the underproduction of ADH in the body. The patients urinate until they dehydrate themselves.
It has two main causes:
- CRANIAL - lack of ADH production
- NEPHROGENIC - receptor resistance
We diagnose it by checking body fluids:
polyuria [excessive urinating] (more than 3L)
polydipsia [excessive thirst] (increased Na+, increased plasma osmolality, decreased urine osmolality, decreased urine Na+)
