Pituitary Gland Dysfunction Flashcards
What pattern of regulation exists for growth hormone?
Pulsatile, Diurnal pattern
Biochemical evaluation requires assessment of _____ and their _____
Pituitary hormones and their target gland hormones
Where is the problem for a primary gland failure?
High trophic hormone level and low target gland level (Target endocrine gland deficiency)
TSH-oma - what kind of failure is this?
Uncommon, easily missed
High target gland hormone and high trophic hormone
Can be:
- autonomous secretion of trophic hormone
- resistance to target gland hormone action
What kind of problem is there for secondary/tertiary gland failure?
Low trophic hormone and low target gland hormone
Trophic Hormone Deficiency
What kind of defect may exist with low trophic hormone level and high target gland hormone level?
Autonomous secretion of target endocrine gland hormone
Dynamic pituitary testing
- Hormone excess assessed by: suppression test (ie oral glucose tolerance)
- Hormone deficiency assessed by: stimulation test (ie insulin tolerance test)
Problems of GH excess
- Gigantism - GH excess before puberty
2. Acromegaly - GH excess after puberty (acral bony overgrowth and soft tissue swelling)
What is the best screening test for GH excess?
Look for an elevated IGF-1 level (make sure that this is age and gender matched).
Integrated 24 hr secretion. Long half-life.
Tx:
- Surgery
- Somatostatin analogs
- GH receptor antagonist
- Radiation therapies
Somatopause
Changes with aging that may make us flabby. Decline of 14% per decade of GH/IGF-1 levels.
Manifestations of adult GHD
Body composition - inc fat deposition - dec muscle mass, strength, & exercis Bone strength - inc bone loss and fracture risk Metabolic and cardiovascular effects - inc cholesterol levels - inc inflammatory and prothrombotic markers (CRP) Psychological well-being - loss of spunk
What is GH not approved for by the FDA?
- Anti-aging
- Obesity
- Chronic fatigue syndrome
How do you diagnose AoGHD?
Provocative test for GH Reserve = Inducing hypoglycemia
- this is dangerous
- do not do in elderly, h/o seizure disorder, CAD, or cerebrovascular disease
Second best test:
GHRH-Arginine test (not available in US), instead we just have Arginine and glucagon stimulation test
Hyperprolactinemia causes
PRL level
Prolactinoma presentation
- Most common functional pituitary tumor
- F:M is 10:1, median age of diagnosis = 34 y/o
Different presentations in men and women
Women: - microadenoma 1 cm - no galactorrhoea - visual field abnormalities - impotence - E.O.M. paralysis (anterior pituitary malfunction)
Diagnosis of prolactinoma
Random PRL level (correlate with tumor size)
> 100-150 ng/dl = microadenomas
> 200-250 ng/dl = macroadenomas
Pituitary MRI
Prolactin deficiency
Etiology: severe pituitary destruction
Presentation: failed lactation in women, no known effect in males
Dx: low basal PRL level
Primary functions of cortisol
- Gluconeogenesis
- Breakdown of fat and protein for glucose production
- control inflammatory reactions
Complications of chronic cortisol excess
Cushings Syndrome
- Changes in carb, protein and fat metabolism
- Changes in sex hormones
- Salt and water retention
- Impaired immunity
- Neurocognitive changes
Endogenous hypercortisolism types and etiologies
ACTH - dependent (70-75%)
- Corticotrope adenoma (Cushing’s)
- Ectopic Cushing’s (ACTH/CRH tumors)
ACTH - independent (25-30%)
- adrenal adenomas
- adrenal carcinoma
- nodular hyperplasia (micro or macro)
What are the high discriminatory features of Cushing’s syndrome?
- Plethoric/moon facies
- Wide (>1cm) violaceous striae (abdominal and axillary)
- Spontaneous ecchymoses
- Proximal muscle weakness
- Early/atypical osteoporosis (atraumatic rib fx)
What are the cortisol rhythms?
- Episodic ACTH/cortisol secretions daily
- Major ACTH/cortisol burst in early morning
- Cortisol Nadir 11-12 pm
Note: most cortisol is bound to transcortin, only 5% is free
Screening tests for Cushing’s
- Disrupted circadian rhythm (midnight salivary or serum cortisol)
- Increased filtered cortisol load (24 hr urine free cortisol)
- Attenuated negative feedback (low dose dexamethasone suppression test)
What is pseudo-cushing’s disease?
- Overactivation of the HPA axis, without tumorous cortisol hyper-secretion (ramps up the whole system)
