Hypopituitarism

About

  • The anterior pituitary releases 6 hormones. LH/FSH/GH/TSH/ACTH and Prolactin
  • The pituitary gland resembles the figure 6

Causes

  • Pituitary adenoma - may be non functioning or functioning and producing a hormone eg Prolactinoma -
  • Craniopharyngioma -Tumour in a child
  • Infiltration - Sarcoidosis, Tuberculosis, Hereditary haemochromatosis
  • Vascular - Sheehan's syndrome and the acute form - Pituitary apoplexy
  • Meningitis, Encephalitis and syphilis
  • Trauma - basal skull fracture
  • Congenital - Kallmann's syndrome - GnRH deficiency + anosmia
  • Autoimmune with Pituitary Antibodies
  • Anorexia, Starvation
  • Radiation damage and chemotherapy
  • Pituitary apoplexy - sudden headache and visual loss and acutely hypopituitarism
  • Empty sella syndrome - pituitary looks empty but just placed eccentrically. Function usually normal

Clinical

  • ACTH - reduced cortisol but preserved mineralocorticoids compared with Addison's disease
  • Prolactin - see above. Loss of ability to lactate. Raised prolactin may be seen if the pituitary stalk is compressed and there is loss of dopaminergic inhibition/
  • LH, FSH infertility, Decreased sex drive, impotence, amenorrhoea
  • Growth hormone- reduced growth and height in before epiphyses fuse. Loss of sense of well being and muscle bulk,
  • TSH - leads to hypothyroidism
  • Pressure can affect posterior pituitary - ADH - Cranial diabetes insipidus
  • Other findings – thin fine wrinkled skin. Truncal fat and reduced muscle bulk. Loss or reduced axially and pubic hair

Local effects of an expanding Pituitary structural lesion

  • Headaches
  • Bitemporal hemianopia
  • Deficiency of local hormones
  • Cavernous sinus extension - III, IV and VI causing ophthalmoplegia and V1 and V2 causing facial pain

Investigations

  • Anaemia and hyponatraemia, hypernatraemia if Diabetes inspidus. Hypoglycaemia if GH deficient
  • Low testosterone, Low T4 and low TSH
  • Deficient cortisol response to ACTH, slight raise prolactin due to stalk effect
  • MRI pituitary - Tumours are Graded by Vertical height on MRI : > 10 mm = macroadenoma , 10 mm = mesoadenoma, < 10 mm = microadenoma. Look for local destructive lesion.

Management

  • Assess and treat cause and consider replacement therapy
  • If patient unwell and you suspect acute hypopituitary then have a low threshold for IV Hydrocortisone
  • L-thyroxine to correct T4 level (not TSH level as is usual)
  • Hydrocortisone orally 15-40 mg per day (give 2/3rds in am is ideal but patients forget so can give it all) Typically hydrocortisone 15 mg am and 5 mg at 4 pm are given.
  • LH/FSH - Males - testosterone if no wish for fertility, Gonadotrophins if fertility wished. Testosterone via im or orally, transdermally or implant for males.
  • LH/FSH - women - oestrogen-progesterone replacement therapy if no wish for fertility. Gonadotropin therapy if fertility wished. Fertility may require Pulsatile GnRH or HCG and FSH
  • Growth hormone is not required in most adult patients. Growth hormones administration may be associated with an increase in malignancy is true.
  • Fludrocortisone and other mineralocorticoids are not usually required in hypopituitarism as there is residual adrenal mineralocorticoid activity independent of the pituitary governed by the renin-angiotensin-aldosterone axis

It is very important to maintain and increase steroids (at least to double) in the event of stress - infection, surgery, trauma, illness

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