Hypothalmic Pituitary Axis Flashcards
What cells make up the anterior pituitary?
- what do they secrete?
Hypothalmic pituitary dysfunction?
What is the most common form of pituitary tumour?
Prolactinoma
Function adenomas of the Pituitary can cause what conditions?
Acromegaly
Cushing’s
Prolactinoma
TSHoma
Acromegaly involves excess secretion of what hormone?
GH
How does Growth hormone act?
Growth hormone acts on the liver causing release of IGF-1 and IGF-BPI.
IGF-1 stimulates femur and muscle growth.
Stimulates glucose release, can also lead to insulin resistance.
What inhibits release of GH?
Somatostatin
What causes acromegaly?
Pituitary adenoma of the somatotroph cells.
Note: Is a benign tumour.
Multiple endocrine neoplasia type 1 aka Wermer syndrome affects what organs?
Parathyroid
Pancreas
Pituitary
Symptoms of acromegaly
Growth of the bones of the hands, feet and lower jaw.
Protrusion of forehead.
Soft tissue swelling in the hands face feet.
Increased size of organs.
Excessive sweating.
These can lead to complications such as:
Carpal tunnel.
Diabetes (diabetogenic effect of GH).
Congestive heart failure (due to heart enlargement).
Gastro intestinal cancers.
Cushing’s
Excess ACTH secretion from pituitary leads to excess cortisol release.
Symptoms of Cushings
High index symptoms of Cushings
Diagnosis and Management of Cushing’s
What effect does dopamine have on the AP?
Dopamine inhibits release of prolactin.
Effects of Prolactin:
- Mammary Gland Development
- Levels increase significantly during pregnancy
- Induce and maintain lactation of the primed breast.
- Lactational Amenorrhea
- Immunomodulatory effectsstimulates lymphocyte growth factor
Diagnosis and management of Prolactinoma
Non-functioning pituitary adenoma’s include:
Null cell adenomas
Gonadotroph adenomas
Clinically silent adenomas
What are NFPA?
- Benign pituitary neoplasms that do not cause hypersecretion of pituitary hormones.
- NFPA is the most common type of pituitary macroadenomas.
What is the treatment for NFPA?
Treatment: Observe if static and patients are asymptomatic. Needs surgery if compressive symptoms on the optic chiasm.
Hypopituitarism:
What is diabetes insipidus?
Diabetes insipidus is a rare condition where you pee a lot and often feel thirsty. Diabetes insipidus is not related to diabetes, but it does share some of the same signs and symptoms. The 2 main symptoms of diabetes insipidus are: extreme thirst (polydipsia) peeing a lot, even at night (polyuria).
What is the treatment for diabetes insipidus?
Vasopressin analogues (Desmopressin)
Cranial/pituitary Radiotherapy: has what effect on the pituitary?
Hypopituitarism
Cranial/pituitary Radiotherapy:
Cranial/pituitary Radiotherapy:
- Hypopituitarism can occur up to 10 years after treatment
- Late effects of cancer treatment
- Observed in childhood cancer survivors
- Low dose radiation- primarily GH deficiency and impaired linear growth and precocious puberty I
- Higher dose radiation -LH/FSH, TSH and ACTH deficiency
Pituitary apoplexy
Haemorrhage and/or infarction of the pituitary gland.
What are the symptoms of pituitary apoplexy?
Clinical features
- Sudden onset of headache
- Vomiting
- Visual impairment
- Decreased consciousness
- Acute hormonal deficiency (ACTH)
Lymphocytic hypophysitis
Autoimmune inflammatory disorder of pituitary.
Lymphocytic hypophysitis (LH) is a condition in which the pituitary gland becomes infiltrated by lymphocytes , resulting in pituitary enlargement and impaired function. It most often occurs in women in late pregnancy or the postpartum period, but can also occur in prepubertal or post-menopausal women, and in men.
Lymphocytic hypophysitis symptoms:
What is the most common cause hypoprolactinaemia?
Other causes?
Sheehan’s syndrome - where lactotroph cells die in women due to postpartum haemorrhage.
Note: Pituitary tumour can damage lactotroph cells due to inflammation.
- Note only causes symptoms in pregnant breast feed mothers.
Hyperprolactinaemia causes:
Other causes:
Symptoms of hyperprolactinaemia in men?
Galactorrhoea / Gynecomastia
ED
Carpal tunnel syndrome and sleep apnoea are classic complications of what endocrine condition?
Carpal tunnel syndrome and sleep apnoea are classic complications of acromegaly.
Acromegaly
Acromegaly is the clinical manifestation of excessive growth hormone (GH). Growth hormone is produced by the anterior pituitary gland.
Most common cause of acromegaly
pituitary adenoma
Paraneoplastic causes of acromegaly
Rarely, acromegaly can also be secondary to a cancer, such as lung or pancreatic cancer, that secretes ectopic growth hormone releasing hormone (GHRH) or growth hormone.
Acromegaly symptoms
Space Occupying Lesion
- Headaches
- Visual field defect (“bitemporal hemianopia”)
Overgrowth of tissues
- Prominent forehead and brow (“frontal bossing”)
- Large nose
- Large tongue (“macroglossia”)
- Large hands and feet
- Large protruding jaw (”prognathism”)
- Arthritis from imbalanced growth of joints
GH can cause organ dysfunction
- Hypertrophic heart
- Hypertension
- Type 2 diabetes
- Colorectal cancer
Symptoms suggesting active raised growth hormone
- Development of new skin tags
- Profuse sweating
Investigations for acromegaly
A random growth hormone level is not helpful as it will fluctuate, giving false positives and false negatives
Insulin-like Growth Factor 1 (IGF-1) is the initial screening test (raised)
Oral glucose tolerance test whilst measuring growth hormone (high glucose normally suppresses growth hormone)
MRI brain for the pituitary tumour
Refer to ophthalmology for formal visual field testing
Treatment of acromegaly
Transpehenoidal surgery
Pegvisomant (GH antagonist given subcutaneously and daily)
Somatostatin analogues to block GH release (e.g. ocreotide)
Dopamine agonists to block GH release (e.g. bromocriptine)
