S8) Pituitary Disorders Flashcards

1
Q

Disorders of the pituitary gland are relatively rare.

What is the most common disorder?

A

The most common cause of pituitary malfunction is a benign tumour (adenoma)

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2
Q

Most pituitary tumours are “non-functioning”.

What does this mean?

A

Non-functioning pituitary tumours contain tumour cells which themselves do not produce any hormone

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3
Q

What is the usual consequence of non-functioning pituitary tumours?

A

These tumours can result in inadequate production of 1/more pituitary hormones due to physical pressure from the growing tumour on glandular tissue

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4
Q

What are the clinical symptoms of non-functioning pituitary tumours?

A

Pressure on surrounding structures in the vicinity of the tumour result in:

  • Headaches
  • Visual problems (optic nerve)
  • Vomiting
  • Nausea
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5
Q

Functional pituitary tumours are quite rare.

What does this mean?

A

Hypersecreting (functional) pituitary tumours contain tumour cells involved in the overproduction of 1/more of the pituitary hormones

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6
Q

What are the clinical symptoms of functional tumours?

A

The clinical symptoms of hypersecreting tumours usually correspond to the systemic effects of the over secreted hormone

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7
Q

Outline the clinical approach in the investigation of a suspected pituitary tumour

A
  • Delineation of the anatomy, size and topographical location of pituitary / parapituitary mass (MRI scan)
  • Assessment of visual field defects
  • Assessment of endocrine function to determine hormonal excess/deficiency
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8
Q

How might one assess the endocrine function in a patient with a suspected pituitary tumour?

A
  • Measure hormone levels in blood
  • Staining sections from a biopsy of the tumour with antibodies for the relevant hormone
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9
Q

What is hypopituitarism?

A

Hypopituitarism is a state of insufficient pituitary hormone production, commonly due to a pituitary adenoma and rarely due to radiation therapy, inflammatory disease or head injury

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10
Q

In light of hypopituitarism, what is the consequence of the adenoma?

A

Progressive loss of anterior pituitary function (GH and LH/FSH first)

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11
Q

What is panhypopituitarism?

A

Panhypopituitarism is the deficiency of all anterior pituitary hormones

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12
Q

Why aren’t ADH and oxytocin secretion usually impaired in hypopituitarism?

A

Secretion of ADH and oxytocin from the posterior pituitary is usually only significantly affected if the tumour affects hypothalamic function

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13
Q

What are some causes of GH deficiency?

A
  • Mass defects from pituitary adenoma
  • Specific gene mutations e.g. GH-releasing hormone receptor
  • Autoimmune inflammation
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14
Q

What are the symptoms of GH hormone deficiency secondary to mass defects from a pituitary adenoma?

A
  • Decreased tolerance to exercise
  • Decreased muscle strength
  • Increased body fat
  • Reduced sense of “well-being”
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15
Q

Why is GH deficiency often difficult to diagnose?

A

GH secretion is pulsatile, deficiency is often difficult to diagnose and a combination of direct and indirect measurements are required

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16
Q

What are the symptoms of Gonadotropin deficiency in men and women secondary to mass defects from a pituitary adenoma?

A
  • Women – infertility, oligomenorrhea, amenorrhea, lack of libido
  • Men – impotence, lack of libido
17
Q

What are some causes of ADH deficiency?

A
  • Hypothalamic tumour
  • Extension of pituitary tumour
  • Cranial radiotherapy
  • Pituitary surgery
  • Autoimmune infiltration
  • Infections e.g. meningitis
18
Q

What is the main consequence of ADH deficiency?

A

Diabetes insipidus – excess excretion of dilute urine resulting in dehydration and an increased sensation of thirst (polydipsia)

19
Q

What is hyperpituitarism?

A

Hyperpituitarism is a state of excess pituitary hormone production mainly due to a functional hypersecreting pituitary adenoma

20
Q

There are three main conditions caused by excess pituitary hormone production from a hypersecreting pituitary adenoma.

Identify them

A
  • Prolactin excess
  • Growth hormone access
  • ACTH excess
21
Q

Hyperprolactinaemia is the most common form of pituitary disorder and can cause a range of symptoms.

Identify five of these

A
  • Galactorrhea (unexplained milk production – rare in men)
  • Gynecomastia (hard breast tissue)
  • Hypogonadism (diminished activity of testes or ovaries)
  • Amenorrhea (cessation of menstrual cycle)
  • Erectile dysfunction
22
Q

What is the most common cause of hyperprolactinaemia?

A

Prolactinoma – a pituitary adenoma that secretes prolactin

23
Q

Identify some physiological causes of hyperprolactinaemia

A
  • Pregnancy
  • Suckling
  • Stress
  • Exercise
  • Drugs (antipsychotics & antidepressants)
24
Q

In four steps, explain how hypogonadism arises as a co-morbidity in hyperprolactinaemia

A

⇒ Increased plasma prolactin

⇒ Higher level of dopamine for negative feddback

⇒ Dopamine inhibits GnRH secretion from hypothalamus

FSH and LH secretion from the anterior pituitary inhibited

25
Q

How is hyperprolactinaemia usually treated?

A
  • Dopamine receptor agonists e.g. cabergoline
  • Trans-sphenoidal surgery (rare)
  • Radiotherapy (rare)
26
Q

Growth hormone secreting pituitary adenomas are typically large (>10 mm in diameter).

In light of this, identify some of its associated symptoms

A
  • Local mass effects – headache, visual field defects and other cranial nerve palsies
  • Systemic effects – increased GH secretion & local IGF-1 production leads to gradual change in physical appearance
27
Q

Describe some the the changes in physical characteristics observed in growth hormone excess

A
  • Coarse facial features: broad nose, thick lips, prominent supraorbital ridge
  • Enlargement of the hands and feet
  • Greasy skin
  • Excessive sweating
  • Deepening of the voice (hypertrophy of vocal cords)
28
Q

Explain why excess GH secretion can be associated with diabetes mellitus

A

GH antagonises the actions of insulin, so diabetes mellitus develops as a metabolic complication

29
Q

Three types of treatment options are available for patients with acromegaly.

Identify them

A
  • Surgery
  • Radiation therapy
  • Drug therapy e.g. dopamine receptor agonists, synthetic somatostatin analogs
30
Q

What is a consequence of excessive ACTH secretion due to a pituitary adenoma?

A

Excess endogenous secretion of ACTH from the anterior pituitary gland is one of the causes of Cushing’s syndrome