Hypopituitarism

Overview

Hypopituitarism describes the decreased secretion of one or more of the hormones secreted by the pituitary gland. If there is a deficiency of most or all of the pituitary hormones, the term panhypopituitarism is used.

The signs and symptoms depend on the hormone affected, the severity of the deficiency, and the speed of onset. 

Causes

• Pituitary tumours (e.g. pituitary adenoma) – most common
• Craniopharyngioma:
  • May affect the hypothalamus which in turn can affect the pituitary gland
• Subarachnoid haemorrhage
• Sheehan’s syndrome
• Pituitary apoplexy
• Iatrogenic (e.g. irradiation/surgery)
• Head injury
• Infiltrative causes (e.g. sarcoidosis, haemochromatosis)
• Idiopathic

Presentation

The presentation depends on what hormone is affected. Features may be:

• Adrenocorticotropic deficiency – see Adrenal Insufficiency:
  • Fatigue
  • Dizziness
  • Nausea
  • Postural hypotension
  • Hypoglycaemia
  • Hyponatraemia
• Thyroid-stimulating hormone deficiency – see Hypothyroidism:
  • Fatigue
  • Cold intolerance
  • Constipation
  • Dry skin
  • Hair loss
  • Weight gain
• Growth hormone deficiency:
  • Fatigue
  • Short stature – if this occurs in children
  • Decreased muscle mass and strength
• Antidiuretic hormone deficiency – see Diabetes Insipidus:
  • Polyuria
  • Polydipsia
  • Hypernatraemia
• Gonadotropin deficiency:
  • In women:
    • Oligomenorrhoea
    • Infertility
    • Reduced libido
  • In men:
    • Impaired sexual function
    • Loss of facial, pubic, and body hair
    • Reduced libido
• Features of an intracranial mass:
  • Headaches
  • Visual field defects (e.g. bitemporal hemianopia for pituitary adenomas)

Investigations

• Hormone profile testing:
  • These are tests according to what deficiencies are suspected (e.g. thyroid function tests, cortisol testing etc.)
• MRI pituitary gland:
  • Assesses the presence of a pituitary adenoma
  • Ideally, blood tests should be performed first as incidental pituitary masses (‘incidentalomas’) may be present, potentially incorrectly suggesting a pituitary mass is a cause

Management

• 1^st-line: manage underlying cause (e.g. surgery) + replace deficient hormones
• Early diagnosis and intervention are associated with a better prognosis
• The presence of complications is associated with a poorer prognosis