Endocrinology: Pathology - Pituitary adenoma

Question 1

Pituitary microadenoma

Answer 1

<1cm diameter

Question 2

Pituitary macroadenoma

Answer 2

> 1cm diameter

Question 3

Most common pituitary adenoma

Answer 3

Lactotroph adenoma (~30%)

Question 4

Hormones produced by lactotroph adenoma

Answer 4

Prolactin

Question 5

Hormones produced by somatotroph adenoma

Answer 5

GH

Question 6

Hormones produced by corticotroph adenoma

Answer 6

ACTH

Question 7

Hormones produced by gonadotroph adenoma

Answer 7

FSH, LH

Most are hormonally silent

Question 8

Hormones produced by thyrotroph adenoma

Answer 8

TSH

Question 9

Least common adenoma

Answer 9

Thyrotroph adenoma (<1%)

Question 10

Hormones produced by plurihormonal adenoma

Answer 10

GH, PRL, TSH

Question 11

Peak incidence of pituitary adenoma

Answer 11

35-60 years

Question 12

Prevalence of pituitary adenoma

Answer 12

~14%

Question 13

Macroscopic characteristics of pituitary adenoma

Answer 13

Typically soft/gelatinous and well-circumscribed
Up to 30% are aggressive adenomas (unencapsulated and infiltrate surrounding tissues e.g. cavernous and sphenoid sinuses, dura, occasionally brain itself)

Question 14

Microscopic characteristics of pituitary adenoma

Answer 14

Cellular monomorphism

Sparse reticulin

Question 15

Clinical features of non-functional pituitary adenoma

Answer 15

Present with symptoms related to mass effect:

1. Radiographic abnormalities of sella turcica
2. Visual field defects (classically bitemporal hemianopia)
3. Signs and symptoms of raised ICP (headache, nausea, vomiting)
4. Hypopituitarism (occasionally)
5. Pituitary apoplexy (rarely)
6. Mild hyperprolactinaemia

Question 16

Why is bitemporal hemianopia the typical VF defect seen with pituitary adenomas?

Answer 16

Proximity of sella turcica to decussating optic nerve fibres at level of optic chiasm

Question 17

Why can mild prolactinaemia be seen in pituitary adenomas that do not produce prolactin?

Answer 17

Due to disturbance of dopamine release from hypothalamus (dopamine has inhibitory effect on prolactin production)

Question 18

Clinical features of lactotroph adenoma

Answer 18

1. Amenorrhoea (causes ~1/4 of all cases of amenorrhoea)
2. Galactorrhoea
3. Loss of libido
4. Infertility

Question 19

Clinical features of somatotroph adenoma

Answer 19

1. Gigantism (in children prior to closure of epiphyses)
2. Acromegaly (adults or children post closure of epiphyses)
3. Wide range of metabolic disturbances including: gonadal dysfunction, diabetes mellitus, generalised muscle weakness, HTN, arthritis, CCF, increased risk of GI cancers

Question 20

How are many of the clinical features of gigantism mediated?

Answer 20

GH stimulates hepatic secretion of IGF-1

Question 21

Clinical features of gigantism

Answer 21

Generalised increase in body size with disproportionately long arms and legs

Question 22

Clinical features of acromegaly

Answer 22

1. Growth of skin and soft tissues; viscera (thyroid, heart, liver, adrenals); and bones of face, hands and feet
2. Hyperostosis (increased bone density) in spine and hips
3. Enlargement of jaw causes prognathism (protrusion) and broadening of lower face

Question 23

How do the symptoms of somatotroph adenoma change with treatment?

Answer 23

Characteristic tissue overgrowth and related symptoms recede with treatment, and metabolic abnormalities improve

Question 24

Clinical features of corticotroph adenoma

Answer 24

1. Cushing syndrome (called Cushing disease when caused by pituitary adenoma)
2. Nelson syndrome

Question 25

What is Nelson syndrome and what causes it? How do patients present?

Answer 25

Development of large destructive pituitary adenoma post-adrenalectomy for treatment of Cushing syndrome Due to loss of inhibitory effect of adrenal corticosteroids on corticotroph microadenoma Hypercortisolism does not result because adrenals are absent, but patients can present with mass effects and with hyperpigmentation due to trophic effects of melanotropin (derived from POMC) on melanocytes

Question 26

Clinical features of gonadotroph adenoma

Answer 26

1. Generally non-functional (most frequently present in middle-aged men and women with neurologic symptoms) 2. Impaired LH secretion (may be due to impairment of function of normal gonadotrophs by adenoma, or by negative feedback of high oestrogens on LH secretion)

Question 27

How does a functional gonadotroph adenoma present?

Answer 27

Decreased testosterone in males (decreased energy and libido) Amenorrhoea in premenopausal females

Question 28

Treatment of lactotroph adenomas

Answer 28

Bromocriptine (dopamine receptor agonist) | Surgery

Question 29

Treatment of somatotroph adenoma

Answer 29

Somatostatin analogues (e.g. octreotide) GH receptor antagonists (e.g. pegvisomant) Surgery

Question 30

Diagnosis of somatotroph adenoma

Answer 30

Elevated serum GH and IGF-1 | GH suppression test (failure to suppress GH production in response to oral glucose load)

Question 31

Hormones produced by mammosomatotroph adenoma

Answer 31

PRL + GH

Question 32

Which cells of the anterior pituitary arle acidophilic and which are basophilic?

Answer 32

Acidophilic: somatotrophs, lactotrophs Basophilic: corticotrophs, thyrotrophs, gonadotrophs