Pituitary adenoma

About

  • Usually benign tumours often asymptomatic arising from the anterior pituitary

Types

  • Prolactinomas are commonest. In females causes loss of periods and infertility. Galactorrhoea. In males there is loss of libido, impotence and infertility and galactorrhoea depending on the prolactin levels. Hypogonadism and osteoporosis.
  • Non secreting adenomas
  • Growth hormone secreting - Acromegaly if after epiphyseal fusion, Giantism if before. See topic
  • ACTH secreting (rare)
  • TSH releasing (very rare)
  • GnRH releasing (very rare)

Pathophysiology

  • The clinical effects of the hormone often predominate
  • Pressure effects can cause headaches and pressure on the optic chiasma and hypopituitarism and stalk effects with mild elevated prolactin as dopamine inhibition blocked
  • Tumours may rarely bleed presenting as headache
  • Damage to posterior pituitary and hypothalamus can cause Diabetes insipidus and obesity
  • Breaches in the dura and sphenoid bone can lead to CSF rhinorrhoea

Hypopituitarism - in usual order

  • LSH/FSH/GH effect with low testosterone and oestrogen. There is loss of libido and secondary sexual characteristics. The testes are small and soft. Skin is smooth and finely wrinkled around the eyes.
  • TSH loss : There is a low T4 and low TSH with pituitary hypothyroidism.
  • ACTH loss: ACTH loss will cause reduced adrenal steroid production. Mineralocorticoid function is intact as it is controlled by the RAA system.
  • Vasopressin loss : Polyuria and polydipsia of Diabetes insipidus

Clinical

  • Check visual fields for Bitemporal hemianopia
  • Morning headache
  • Stalk effect - compression of pituitary stalk leads to loss of dopamine inhibition on pituitary and rise in prolactin
  • Non functioning - headache and visual effects
  • Prolactin excess - reduces testosterone and causes mild gynaecomastia and in some cases galactorrhoea

Investigations

  • Assess pituitary function. Check testosterone, LH, FSH, TSH. Check IGF-1 if Acromegaly suspected.
  • MRI pituitary views - assess size and extrasellar extension.
  • Using vertical height classify as those > 10 mm = macroadenoma. 10 mm = mesoadenoma and under 10 mm are microadenomas

Histology of Adenomas

  • Cells can be divided by staining. However immunofluorescence and other markers are used nowadays
  • Chromophobes (usually non secretory)
  • Chromophils - Basophils (ACTH, LPH, TSH,FSH,LH,MSH) and Acidophils (PRL, GH)

Management

  • Prolactinoma are the only pituitary tumour where medical rather than surgical management is first line. They respond well to low dose dopamine agonists such as bromocriptine and cabergoline. The tumour shrinks in size and over time the treatment can be withdrawn with regular follow up by measuring prolactin and MRI.
  • Acromegaly (see subject)
  • Large tumours causing pressure effects or hormonal effects and unresponsive to other methods can be treated by surgery or radiotherapy. Some may be removed by transphenoidal surgery. Larger ones can need Transfrontal surgery.
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