Endocrinology Flashcards
6 anterior pituitary hormones
GH, TSH, ACTH, FSH, LH, prolactin
Threshold osmolality when ADH released
283 mOsm/kg (thirst at 295)
GH - stimulated by what factors
Sleep, stress, haemorrhage, fasting, hypoglycaemia, exercise (30 mins post exercise)
Conditions associated with GH excess
- McCune Albright
- Carney complex
ACTH time of peak release
3-4 am (nadir at 10-11pm)
Factors which increase prolactin secretion
Sleep, stress, lactation, nipple stimulation, anti-dopaminergic drugs (inc metoclopramide, TRH (therefore elevated in hypothyroid)
Craniopharyngoma symptoms
- Anterior pituitary hormone deficiencies
- Growth failure, DI (eg polyuria, polydipsia, nocturia), visual symptoms
Septo-optic dysplasia triad
- Optic nerve abnormality (absent optic chiasm +/- optic nerve hypoplasia)
- Agenesis or hypoplasia of the septum pellucidum +/- corpus callosum
- Variable hypothalamic insufficiency
Congenital facial features suggestive of GH deficiency
Midline anomalies eg cleft lip/palate, or single maxillary incisor
Congenital GH deficiency - presenting features
- Normal length & wt at birth but drop by 1 yr of age (if severe) - red flag = falling off curve age 3
- Round head, broad face, prominent frontal bone, depressed saddle shaped nose, bulging eyes, sparse facial axillary and pubic hair
GH deficiency diagnostic tests
- IGF-1 and IGF-BP3 (IGF binding protein) (GH def unlikely if on upper limit of N)
+ - FBC, ESR, CRP
- Metabolic panel
- Coeliac screen
- Free T4/TSH
- Growth velocity
- Bone age
- GH stimulation testing
MPH calculation
Constitutional gth - key features
- Normal gth velocity and DELAYED bone age
- Tracks MPH expected for the family
- GH and other studies are normal
- Bone age mirrors height age instead of chronological age
- Often associated with delayed puberty
- Expected to meet full height potential
Genetic (familial) short stature - key features
- Normal gth velocity and normal bone age
- Usually family hx
- Tracks at predicted MPH
GH deficiency short stature - key features
DECREASED gth velocity and DELAYED bone age
Syndromic causes short stature
- Noonan
- Turner
- Williams
- 22q11 deletion
- Cornelia de Lange
- Fanconi anaemia
- Prader Willi
- Russell Silver (with relative macrocephaly)
- Skeletal dysplasias eg achondroplasia
Non-syndromic causes short stature
- Systemic disease - IBD, coeliac, HIV, anaemia, renal
- Hypothyroidism
- Adrenal insufficiency and excess
- Psychosocial - stress, emotional deprivation
- Idiopathic - normal GH secretion
- SHOX gene deletion
Madelung deformity
A/w SHOX (SHOX a/w Turner)
*Slowed gth of distal radius -> shorter, curved
*Dislocation of the ulna, causing dorsal subluxation and prominent ulnar head
*Radial deviation of the wrist
*Triangular carpal bones
Test to order before commencing Prader Willi on growth hormone
Sleep study (polysomnography) - risk of resp compromise and death
Things to monitor on GH treatment
- SCFE
- IIH
- Transient CHO intolerance
- Transient hypothyroidism
- Scoliosis
- No increased risk of leukaemia
Diagnostic criteria DI
- Serum osmo > 300 mOsm/kg and urine osmo <300 mOsm/kg pathognomonic
- Serum ADH or COPEPTIN
- Water deprivation test
- Also urine specific gravity <1.005 and urine osmo <200 mOsm/kg
Central DI - key feature
No increase in ADH despite increase in plasma osmolality (aka no posterior pituitary release)
Peripheral (nephrogenic) DI - key feature
- Lack of response to ADH by collecting tubules -> dilute urine.
- No increase in urine osmolality despite increasing ADH
SIADH diagnostic criteria
~Dilute blood & concentrated urine~
* Low serum osmolality (<275 mOsm/kg)
* High urine osmolality (>100 mOsm/kg)
* Euvolaemia
* Increased urine sodium (>20 mmol/L)
* no other cause for hyponatraemia
Describe cerebral salt wasting
- Excess secretion of atrial natriuretic peptide (ANP) - released in hypervolaemia
- Promotes salt and water excretion & lowers BP
- Causes - CNS tumours, head trauma, hydrocephalus, CVA
- Signs - high UO & hypovolaemia
- Labs - low serum Na, high urinary Na, low ADH, high ANP
- Rx - 3% NaCl
Cerebral salt wasting v SIADH
Syndromic causes tall stature
- Klinefelter
- Marfan
- Homocystinuria
- Beckwith Wiedeman
- Sotos syndrome
Key features Sotos syndrome
- Facies - long narrow face, high forehead, small pointed chin
- Premature eruption of teeth, strabismus, ASD
- NSD1 gene
- Accelerated growth until 4-5 yrs, then bone age correlates
- Normal adult height
- Puberty at normal time
- Big hands and big feet, present as clumsy
- Mild ID
Symptoms prolactinoma
In kids (macroademona) - visual defects esp bitemporal hemianopia, blurred or loss of vision
In adolescents - headache, amenorrhoea, galactorrhoea
PTH regulation
STIMULATED by HIGH phosphate and LOW Ca
INHIBITED by calcitriol (active Vit D) and calcitonin (released by parafollicular cells in thyroid)
Vit D and PTH effects on Ca and PO4
- High Vit D -> high Ca + high PO4
- Low Vit D -> low Ca and low PO4
- High PTH -> high Ca and low PO4
- Low PTH -> low Ca and high PO4
Vit D synthesis
- Skin (UV) - 7-dehydrocholesterol → Pre-vit D3 → Vit D3
- Liver: Vit D3 → 25-hydroxyvit D (calcidiol)
- Kidneys: 25(OH)D → 1,25-dihydroxyvitamin D (1, 25-(OH)2-D, calcitriol, active form)
Actions of Vit D
*Increases Ca and PO4 absorption in small intestine (more serum Ca)
*Increases renal tubular Ca and PO resorption (prevents excretion in urine)
*Increases Ca resorption from bone (stimulates osteoclasts) (less significant affect than intestinal absorption)
