Hypersecretion of anterior pituitary hormones Flashcards
What are the main causes of hyper-secretion of adenohypophysial hormones?
Pituitary adenoma
Tumours from non-endocrine tissue (ectopic in origin)
What visual field defect is associated with pituitary adenoma, and why?
Bitemporal hemianopia
Due to compression of the optic chiasm by growth of suprasellar tumour
State the disease resulting from hypersecretion of:
a. Corticotrophin
b. Thyrotrophin
c. Gonadotrophin
d. Prolactin
e. Somatotrophin
Cushing's disease Thyrotoxicosis Precocious puberty in children Hyperprolactinaemia Gigantism, Acromegaly
State when hyperprolactinaemia may be physiological and when it may be pathological
Physiological = pregnancy, breastfeeding
Pathological = prolactinoma (often microadenomas < 10mm diameter); most common functioning pituitary tumour
**High prolactin suppresses GnRH pulsatility
State the symptoms of hyperprolactinaemia in women
- Galactorrhoea (milk production)
- Secondary amenorrhoea (or oligomenorrhoea)
- Loss of libido
- Infertility
State the symptoms of hyperprolactinaemia in men
- Galactorrhoea uncommon (since appropriate steroid background usually inadequate)
- Loss of libido
- Erectile dysfunction
- Infertility
How does dopamine affect prolactin secretion
Dopamine released from hypothalamic dopaminergic neurones bind to D2 receptors on lactotrophs, inhibiting prolactin release
How is hyperprolactinaemia treated?
Oral administration of dopamine receptor (D2) agonists - decrease prolactin secretion and reduce tumour size
Give two examples of dopamine receptor (D2) agonists
BROMOCRIPTINE
CABERGOLINE
List some side effects of dopamine receptor agonists
Nausea and vomiting Postural hypotension Dyskinesias Depression Impulse control disorder e.g. pathological gambling, hyper sexuality
Excess growth hormone in childhood results in ………….
GIGANTISM
Excess growth hormone in adulthood results in ………….
ACROMEGALY
What are the most serious complications of excess growth hormone?
Cardiovascular disease 60%
Respiratory complications 25%
Cancer 15%
Describe the onset of acromegaly
Insidious
What grows in acromegaly?
- Periosteal bone
- Cartilage
- Fibrous tissue
- Connective tissue
- Internal organs (cardiomegaly, splenomegaly, hepatomegaly, etc.)
State the clinical features of acromegaly excessive sweating
- Excessive sweating (hyperhidrosis)
- Headache
- Enlargement of supraorbital ridges, nose, hands and feet, thickening of lips and general coarseness of features
- Macroglossia
- Prognathism
- Carpal tunnel syndrome (median nerve compression)
- Barrel chest, kyphosis
How might a patient help with the diagnosis of acromegaly
Patients can bring old photos
What is the metabolic effect of acromegaly?
Excess GH => increased endogenous glucose production,
decreased muscle glucose uptake => increased insulin production => increased insulin resistance => impaired glucose tolerance => DIABETES MELLITUS
What other complications are there associated with acromegaly?
- Obstructive sleep apnoea
- Hypertension (GH mediated renal sodium reabsorption)
- Cardiomyopathy (due to hypertension, DM or direct toxic effects of excess GH)
- Increased risk of cancer
What other anterior pituitary hormone may be co-secreted in high amounts with GH, especially in younger patients?
Prolactin
How is acromegaly diagnosed biochemically?
Elevated serum IGF-1 following oral glucose load (oral glucose tolerance test) due to failed suppression/paradoxical rise in GH
Summarise the treatment of acromegaly
1st LINE:
- Surgical removal of tumour (trans-sphenoidal)
MEDICAL:
- Somatostatin analogues e.g. OCTREOTIDE; sub cut/monthly depot injection
- Dopamine receptor agonists (because GH secreting pituitary tumours frequently express D2 receptors)
RADIOTHERAPY (especially for large tumours)
State the side effects of somatostatin analogues, and when specifically might it be used
‘Endocrine cyanide’
- GI side effects common (e.g. nausea, diarrhoea, gallstones)
Used before surgery for ease of resection, and post-operatively if not cured or during radiotherapy
