Pituitary 1 Flashcards
What 2 hormones are released from the Posterior Pituitary?
- Oxytocin
- ADH
Where is the pituitary located?
Which cranial nerves?
Sits in sella turcica of sphenoid bone
3, 4, 5, 6
Which method of testing is used for majority of tests run on blood?
Venipuncture
Describe a 24 hour urine
- Measurement of what 2 things for Pheochromocytoma?
- Discard the first morning void
- Collect for next 24 hours (including void at end of 24 hours)
- Record last voiding time
- Keep urine cool
- If ANY urine is lost, discard entire specimen, begin collection again next day
- Pheo: catecholamines & metabolites
What is being measured?
- Hormone w/ longer half life
- NOT bound by proteins
- Measured directly w random test
TSH
What is being measured?
- Hormones BOUND to proteins (albumin & binding proteins)
Free & total fractions
Total T4 and Free T4
When should cortisol be measured and how?
Blood, perform first venipuncture between 6 am - 8am
(cortisol is highest in the AM)
What type of test do you use?
- Hyperfunctioning of gland is suspected
- Pt w/ excess cortisol
Suppression test
- Dexamethasone suppression test (synthetic glucocorticoid)
Which test do you use?
- Test for HYPOfunctioning gland
- Pt w/ low cortisol
Stimulation test
- ACTH stimulation test (tests adrenals response to ACTH)
What is the most abundant pituitary hormone?
Growth Hormone (GH)
Somatotrope cells
GH secretion is controlled by what 2 factors?
- Hypothalamic
- Peripheral
What do GHRH and GHIH do?
- GHRH: stimulates GH secretion
- GHIH: (somatostatin) inhibits GH secretion
T/F
- GH secretion is pulsatile and is undetectable between pulses
True
When is GH at its peak?
Within an hour after the onset of DEEP SLEEP
What is produced in the liver after stimulation of GH?
GH stimulates what type of growth in children?
- IGF-1
- linear growth
What stimulates growth of epiphyseal plates of long bones?
IGF-1
Absence of IGF-1 produces what condition?
Dwarfism (Laron type dwarfism)
What are the 3 phases of post-natal growth?
- Infantile
- Childhood
- Pubertal
Which post-natal growth phase?
- Rapid growth
- first 2 yrs of life
- 30-35 cm
Infantile phase
Which post-natal growth phase?
- Growth is constant (5-7 cm/yr)
- Slight slowing later in childhood “prepubertal dip”
Childhood
Which post-natal growth phase?
- Growth spurt of 8-14 cm/yr
- Effects of increasing gonadal steroids/GH secretion
Pubertal Phase
Velocity falls to what number when approaching final adult height?
0
Definition of what?
◦Variation of normal
◦2 SDs or more below the mean height for children of that sex and chronologic age
Constitutional Short Stature
Definition of what?
◦Constitutional short stature in children of short parents
Child is growing within the parental target range
Growth curve is consistently at or below the 3-5th percentile
Growth velocity is typically normal
Genetic Short Stature
What are 6 pathologic causes of short stature?
- GH deficiency
- IUGR
- Infections (rubella, CMV)
- Maternal drug/alcohol usage
- Genetic syndromes (Turner’s syndrome, etc.)
- Chronic systemic disease (cancer, cystic fibrosis, renal insufficiency, GI disease)
- Psychosocial dwarfism – poor growth associated with emotional and nutritional deprivation
What are 3 basic steps to dx short stature
- H&P
- IGF-1 levels
- GH stimulation tests (DEEP SLEEP)
What are 4 MC reasons a pt might have noticeable dysmorphic features / disproportionate short stature?
- Chromosomal abnormalities (Trisomy 21/Turners)
- Intrauterine infections
- Maternal exposures (toxins, ETOH, smoking)
- Disproportionate short stature (Skeletal dysplasia or Rickets)
What are some “genetic factors” which could lead to short stature? (3)
- Height of relatives
- Health problems in family
- Hx of early/late puberty in family members
Dx of Short Stature
Does the child have growth failure?
- Children should grow __ cm / year from age 2 y/o until onset of puberty
- What 2 structures should be x-rayed to compare bone development to height & chronological age? (bone age vs. chronological age)
- 5cm
- Hand & wrist
A patient’s H&P suggests GH deficiency.
What is the next step in diagnosing short stature?
Measure plasma IGF-1 levels
(concentration of IGF-1 reflects concentration of secreted GH)
(IGF is stable during the day w/ serum half life of 12-16 hrs)
In what 4 circumstances would IGF-1 levels be lowered, but GH is normal?
- Poor nutrition
- Hypothyroidism
- DM
- Renal Failure
Dx of short stature
- What is “GOLD STANDARD” in dx of GH deficiency and is used when IGF-1 is low?
GH stimulation tests (2 types)
Which GH stimulation test?
- Measure serum glucose and serum GH before and 15, 30, 60, 90 and 120 minutes after the injection of insulin
Insulin induced hypoglycemia
Which GH stimulation test?
- Measure serum GH at 0, 30, 60, 90 and 120 minutes
Arginine
What should be corrected before doing any GH stimulation tests??
Thyroid deficiency
What are 2 hypothalamic causes of GH deficiency?
Idiopathic ↓ GHRH secretion
Hypothalamic tumors
What are pituitary causes of GH deficiency?
Pituitary tumors
Trauma
Surgical removal
Irradiation
Idiopathic
Secretion of abnormal GH molecules
Psychosocial Dwarfism is due to what?
Severe neglect
What is a pharm tx option for GH deficiency in children?
Humatrope Pen
- Synthetic GHRH (if pituitary capable of producing GH)
Depot- 1 - 2 doses/month - 3x/week - daily therapy
- Multiple dose pen devices
- MC sub-q administration of Somatropin!
Growth Hormone Therapy in Children
- Continue therapy until when?
- May develop normal GH secretion…
- Stimulatory effects of which hormones?
- When should GH be retested?
- Children w/ what rarely recover GH as an adult?
- Until growth ceases
- gonadal steroid hormones
- after completion of growth
- multiple pituitary hormone deficiencies
Summary of Short Stature Management:
- Get a good H&P!!
- FOLLOW growth curves!
- If suspicious for pathologic short stature, follow what 4 steps?
- Obtain bone age w/ wrist x-ray
- IGF-1
- Confirm w/ GH stimulation test
- Refer to pediatric endocrinologist
