Hypersecretion of Anterior Pituitary Hormones Flashcards
What is the usual cause of hypersecretion of anterior pituitary hormones?
Pituitary adenoma
What visual defect is associated with pituitary adenoma?
Bitemporal hemianopia
State the disease resulting from hypersecretion of:
a. Corticotrophin
b. Thyrotrophin
c. Gonadotrophin
d. Prolactin
e. Somatotrophin
a. Cortictrophin Cushing’s disease b. Thyrotrophin Thyrotoxicosis c. Gonadotrophins Precocious puberty in children d. Prolactin Hyperprolactinaemia e. Somatotrophin Gigantism/Acromegaly
What is the usual cause of hyperprolactinaemia?
Prolactinoma
Most commonly microadenomas (< 10 mm)
State the symptoms of hyperprolactinaemia.
Loss of libido
Infertility
Galactorrhoea (rarely occurs in males as well) Oligomenorrhoea/amenorrhoea Impotence (in men)
State two physiological causes of hyperprolactinaemia.
Pregnancy
Breast feeding
What does excess growth hormone cause in children and in adults?
Children – gigantism
Adults – acromegaly
What are the most serious complications of excess growth hormone?
Cardiovascular problems (majority) and respiratory problems This is mainly due to organ growth
State some common clinical manifestations of acromegaly.
Prognathism Enlarged supraorbital ridges Enlarged soft tissue Hyperhydrosis Carpal tunnel syndrome (due to excessive cartilaginous growth) General coarseness of features Hypertension macroglossia barrel chest Kyphosis (abnormal rounding of upper back)
What are the metabolic effects of acromegaly?
Increased endogenous glucose production and decreased muscle glucose uptake
Increased insulin response to oral glucose leading to insulin resistance
This causes impaired glucose tolerance (in 50%) and diabetes mellitus (in 10%
What type of test is used to diagnose a hyperpituitary disorder?
Suppression test
What test is used to diagnose acromegaly and how are the results interpreted?
Glucose-induced suppression of growth hormone secretion
Giving glucose should cause a decrease in growth hormone release in a normal individual
In someone with acromegaly, giving glucose will cause a paradoxical rise in growth hormone release
State some of the treatments for acromegaly.
Transsphenoidal Hypophysectomy Radiotherapy Chemotherapy: Octreotide (somatostatin analogue) Bromocriptine and Cabergoline (dopamine receptor agonists)
What are the clinical uses of octreotide?
It can be used short-term before surgery to shrink the size of the pituitary adenoma
It can be used long-term if it can’t be controlled by other means
It is used as a treatment for other neuroendocrine tumours e.g. carcinoid tumours
Describe the administration, distribution and metabolism of octreotide.
Octreotide is administered SC or IM 3/day
It is retained in extracellular fluid
Half-life = 2-4 hours
State some of the side effects of octreotide.
GI tract disturbance (because somatostatin is produced by the small intestine as well)
Initial reduction in insulin secretion causing hyperglycaemia (octreotide inhibits the production of insulin by the beta cells)
Rarely gallstones
What is used to treat hyperprolactinaemia?
Dopamine agonists – bromocriptine and cabergoline
Describe the pharmacokinetics and side-effects of bromocriptine.
Administered orally 1/day Heavily plasma protein bound Half-life = 7 hours (hepatic metabolism) Side effects: Nausea/vomiting/abdominal cramps Dyskinesias (impaired voluntary movement) Psychomotor excitation Postural hypotension Vasospasm in fingers and toes
State some other uses of bromocriptine.
Suppression of lactation
Cyclical benign breast tumours (and cyclic breast pain)
Also used in acromegaly but doesn’t have the same beneficial effect on tumour size
Parkinson’s disease
Describe the pharmacokinetics and side-effects of cabergoline.
Taken orally 1-2/week
Half-life = > 45 hours
Side effect: same as bromocriptine but less pronounced
Describe the visual field in a bitemporal hemianopia
Loss of peripheral vision of both eyes
What is an ectopic tumour?
Tumours that are producing pituitary hormones but are not tumours of the pituitary.
E.g. Ectopic Cushing’s syndrome
What effect does high prolactin have on GnRH?
Suppresses the GnRH pulsatility.
What has dominant control over prolactin release?
Dopamine that acts on D2 receptors of the lactotroph.
What are the general side effects of dopamine agonists?
Nausea and vomiting Postural hypotension Dsykinesias Depression Pathological gambling.
What are some complications of acromegaly?
Obstructive sleep apnoea - Upper airway bone and soft tissue changes leads to narrowing and collapse during sleep
Hypertension - Direct effects of GH/IGF-1, GH mediated sodium reabsorption
Cadiomyopathy - Hypertension, toxic effects of GH on myocardium
Increased risk of cancer - GH is a cell stimulant, colonic polyps regular screening with colonoscopy.
What other hormone is often high in acromegaly?
Prolactin - tumour may secrete both hormones
Hyperprolactinaemia will cause secondary hypogonadism
