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Pituitary Osteo Labs

Endocrine

QuestionAnswer
Prolactin >200: due to: Hyperprolactinemia; Pit Adenoma; Renal Fail; PG
Acromegaly Dx Elevated IGF-1; GH Fails to Suppress <2 ng/mL after 75 g CHO load
If suspect pt is hypocalcemic, measure 1,25-D? No; measure 25-OH D
Looser zones & Milkman lines on xray = Pseudofractures (seen in osteomalacia)
Pituitary adenoma diagnosed by: CT or MRI of brain to evaluate sella turcica
GH lab testing GH on fasting AM samples (often not diagnostic); GH Stim tests (hyperglycemia normally suppresses GH secretion); GH remains elevated in acromegaly
IGF-1 levels influenced by: nutrition (low in malnutrition)
ADH measurement usually unmeasurable; 2.3-3.1 pg/mL
SIADH labs: low serum osmolality, low serum sodium & high urine osmolality
ADH problems: tests DI: H2O deprivation test (pos if central DI); SIADH: water loading test
Water loading study results (1L H2O; hourly urine/serum x 5 hrs) Normal: urine osmo < serum osmo; SIADH: urine osmo > serum osmo
Pituitary dwarfism: IGF-1 & GH Useful to compare IGF-1 levels to GH; IGF-1 is low whenever GH is deficient; IGF1 more stable than GH; mediate GH fx on sk mx
DEXA used for: PA spine, lateral spine, hip, forearm, total body
Quantitative CT bone scan used for: spine (trabecular only)
Osteomalacia labs Low serum Ca, PO4, 25-OH vit D. High PTH and alk phos. Check renal labs.
Transvers radiolucent markings on imaging (pseudofractures) suggest: Osteomalacia
Paget disease labs High alk phos (2/2 osteoblast activity). Ca & PO4 normal. Urinary pyridinolines or N-telopeptide.
Paget disease imaging increased uptake on technetium bone scan. Early dz: lytic lesions on x-ray; later, coarse, dense, chaotic, deformed cortical bone
PCOS LH:FSH ratio >2.0 common
Hirsutism / virilization: lab eval Serum testost (total & free); androstenedione (>1000: ovar adrenal neoplasm); DHEAS (>700: adrenal source of androgen xs; Need adrenal CT to detn if hyperplasia or ca)
Hirsutism / virilization: Imaging Pelvic Exam & US; Abd CT (esp adrenal glands/ fine cuts): adenoma / ca / hypertrophy
gene for achondroplasia FGFR3
central diabetes insipidus confirmed by vasopressin challenge test (pos if reduced UOP)
Paget dz labs high alk phos & urine Ca; normal serum Ca & PO4
Paget disease on x-ray dense, expanded bone; fissures in long bone
Osteoporosis: bone turnover markers Urine N-telopeptide, pyridinium crosslinks, serum osteocalcin. All used to monitor response to tx; should decrease >35% in 3 months
Created by: Abarnard