Hypersecretion of anterior pituitary hormones Flashcards
Hyperprolactinaemia causes
Physiological: pregnancy, breastfeeding
Pathological: prolactinoma (tumour of the lactotrophs)
-prolactinomas are often microadenomas <10mm in diameter
-prolactinomas are the most common functioning (hormone secreting) pituitary tumour
Female hyperprolactinaemia presentation
- galactorrhoea (milk discharge from nipple unrelated to normal lactation)
- secondary amenorrhoea (or oligomenorrhoea)=reason why hyperprolactinaemia often diagnosed earlier in females compared to males
- loss of libido
- infertility
Male hyperprolactinaemia presentation
TEND TO PRESENT WITH SYMPTOMS OF TESTOSTERONE DEFICIENCY
- galactorrhoea (uncommon since not enough oestrogen to prime the breasts for lactation)
- loss of libido
- erectile dysfunction
- infertility
Side effects of dopamine receptor (D2) agonists
- N&V (common with Bromocriptine)
- Postural hypotension (common with Bromocriptine)
- Dyskinesias
- Depression
- Impulse control disorder eg: pathological gambling, hypersexuality, compulsive eating etc
Gigantism
Excess growth hormone in childhood
- no epiphyseal closure so height increases
- typically caused by benign GH secreting pituitary adenoma (tumour of the somatotrophs in the anterior pituitary gland secreting excess GH)
Acromegaly
Excess growth hormone in adulthood
- growth plates fused so no height increase but everything else grows (eg: soft tissue)
- typically caused by benign GH secreting pituitary adenoma (tumour of the somatotrophs in the anterior pituitary gland secreting excess GH)
Growth in acromegaly
NO HEIGHT INCREASE (GROWTH OF REST, PARTICULARLY SOFT TISSUE)
- periosteal bone
- cartilage
- fibrous tissue
- connective tissue
- internal organs (cardiomegaly, splenomegaly, hepatomegaly etc)
Acromegaly clinical features
- excessive sweating (hyperhidrosis)
- headache
- enlargement of supraorbital ridges, nose, hands and feet, thickening of lips and general coarseness of features
- enlarged tongue (macroglossia)
- mandible growth causing protrusion of lower jaw (prognathism)
- carpal tunnel syndrome (median nerve compression)
- barrel chest
- kyphosis
Metabolic effects of acromegaly
- GH is a stress hormone released in response to hypoglycaemia
- Excess growth hormone leads to increased endogenous glucose production and decreased muscle glucose uptake
- the combination of increased insulin production (decreases blood sugar) and increased insulin resistance leads to impaired glucose tolerance and thus diabetes
Complications of acromegaly
- Obstructive sleep apnoea (bone and soft tissue changes surrounding upper airway lead to narrowing and subsequent collapse during sleep)
- Hypertension (direct effect of GH and/or IGF-1 on vascular tree, GH mediated renal sodium reabsorption)
- Cardiomyopathy (hypertension, diabetes mellitus, direct toxic effects of excess GH on myocardium)
- Increased cancer risk (colonic polyps, regular screening with colonoscopy)
Acromegaly diagnosis
- GH levels pulsatile (dependent on time of day) so random measurement in clinic is not useful/unhelpful
- CLINICAL HALLMARK: elevated serum IGF-1 (high GH production signals liver to synthesise lots of IGF-1)
- failed suppression of GH following oral glucose load (oral glucose tolerance test)-> patient with acromegaly shows paradoxical rise
Acromegaly treatment
-First line of treatment is trans-sphenoidal surgery to remove tumour (remove by burrowing through nose and piercing cribriform fascia to get to pituitary tumour)
Medical treatment: Somatostatin analogues (eg: Octreotide->mimics somatostatin which reduces GH secretion from anterior pituitary tumour, shrinking the tumour size which is helpful pre-surgery) and Dopamine agonists (eg: Cabergoline->GH secreting pituitary tumours frequently express D2 receptors even if they do not secrete prolactin themselves. Cabergoline used in short-term pre-surgery)
- Radiotherapy (post-surgery if not all of large pituitary tumour removed from operation)
- last case scenario uses GH receptor antagonists (eg: Pegvisomant)->GH levels remain the same but IGF-1 levels reduced as effect of GH is blocked
Somatostatin analogues
- ‘endocrine cyanide’->stops everything, including GH secretion
- administered by injection: subcutaneous (short acting) or monthly depot
- not ideal as long term solution
- GI side effects common (nausea, diarrhoea, predisposition to gallstones)-> switches off digestive peptides essential for gut
- works to reduce GH secretion and tumour size
- reduces tumour size so pre-treatment before surgery can make resection easier
- Analogue can be used post-operatively if not cured (not all tumour removed) or whilst waiting for radiotherapy to take effect (works slowly)
Hyperpituitarism cause
-Usually isolated pituitary tumour but can be ectopic in origin
Hyperpituitarism symptoms
ASSOCIATED WITH EXCESS PRODUCTION OF ADENOHYPOPHYSIAL HORMONES (dependent on cell type in
