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)
