Pituitary gland diseases: acromegaly, hypercortisolism (Itsenko Cushing syndrome), hypopituitarism, diabetes insipidus. Etiology & pathogenesis. Organ-site pathomorphology
What is the pituitary gland
- A bean-shaped structure at the base of the brain within sella turcica. Has an anterior and a posterior part
- Anterior (adenohypophysis)
- Adrenocorticotropic hormone (triggers cortisol release from adrenals)
- Follicular stimulating hormone (stimulates ovarian development and spermatogenesis in females and males respectively)
- Growth hormone (growth)
- Luteinizing hormone (triggers ovulation)
- Prolactin (triggers milk production)
- Posterior (neurohypophysis)
- Oxytocin
- Vasopressin
- The anterior portion releases true hormones, while the posterior part releases neurohypophysial hormones into the blood
- The pituitary is under the control of the hypothalamus (which sits above attached by the stalk), which releases control hormones
Symptoms of pituitary gland diseases have three groups:
- Hyperpituitarism effects - often due to anterior pituitary adenoma
- Hypopituitarism effects - often due to deficiency of trophic hormones (pituitary or, less often, hypothalamic damage), possibly due to ischemia, surgery, radiation or inflammation
- Local mass effect
Acromegaly and Hypercortisolism
- Both of these are due to overproduction of pituitary hormones. Growth Hormone in the case of acromegaly, and adrenocorticotropic hormone in the case of hypercortisolism
- The most common cause of this is pituitary adenoma
- Increased GH is due to a Somatotroph pituitary cell tumour, the tumour can be densely or sparsely granulated. In children increased GH causes gigantism, in adults, increased GH causes acromegaly. Acromegaly presents as enlarged hands and feet, possibly with joint pain, thicker skin and forehead enlargement. Also display impaired glucose tolerance and diabetes mellitus
- Increased ACTH causes hypercortisolism, the condition is known as Cushing syndrome (Cushing disease when caused by a pituitary adenoma). Symptoms are abdominal obesity, round, reddish (moon) face, fat lump between shoulders, acne, fragile skin and high BP.
- Most pituitary adenomas are sporadic (non-familial) and some do not have any effect on the hormone production.
- Pituitary adenoma is usually well circumscribed, commonly confined by sella turcica, although larger lesions may press on the optic chiasm. Cellular monomorphism and no reticulin network distinguish pituitary adenoma from non-neoplastic anterior pituitary parenchyma.
H&E, GH-secreting (somatotroph) adenoma: a monotonous sheet of one cell type with pink (acidophilic) cytoplasm, unlike the mixed cells of normal anterior pituitary.
Image: “Pituitary adenoma (1) GH production” by No machine-readable author provided. KGH assumed (based on copyright claims)., CC BY-SA 3.0, via Wikimedia Commons.
Remember: a macroadenoma growing up out of the sella compresses the crossing nasal fibres in the optic chiasm, so the classic visual defect is bitemporal hemianopia (loss of both outer visual fields).