Pituitary hyperplasia

Type

Physiologic

• Puberty
• Young menstruating female
• Pregnancy
• Lactation
• Exogenous estrogen treatment

Pathologic

End-organ failure

• Primary hypothyroidism (M/C cause of pathologic hyperplasia)
• Primary gonadal failure

Imaging features

• Diffuse, symmetric pituitary enlargement with convex superior margin.
• Homogeneous enhancement, no focal nodule, no cavernous sinus invasion.
• Stalk midline and normal thickness (key vs hypophysitis/adenoma).

CT

No bone erosion.

MRI

• Can contact optic chiasm.
• Isointense with cortex on both T1-and T2WI.
• shape preserved, just ‘plump’

Differential diagnosis

• Macroadenoma
  • Often focal/off-midline mass, heterogeneous, can invade cavernous sinus.
• Lymphocytic hypophysitis common in pregnant and postpartum
  • Other causes of hypophysitis e.g. IgG4-related, drug-related hypophysitis
  • Thick, non-tapering stalk, often loss of posterior bright spot, DI more common.
• Intracranial hypotension
  • Engorged pituitary
  • Brain sagging
  • Pachymeningeal enhancement
  • Small ventricles