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Pituitary Osteo Labs
Endocrine
| Question | Answer |
|---|---|
| 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
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