Clinical Chemistry

Anterior pituitary

 

Acidophils –> produce ?

Prolactin and GH-secreting cells

 

” drink lactic acid to grow”

Posterior pituitary

Which hormones

ADH & oxytocin
Most common secretory tumors of the pituitary

Prolactinomas

~ microadenomas <1cm

Causes of panhypopituitarism

Impinging: Nonsecretory pituitary adenomas, Craniopharyngeomas

Infarction: Sheehan syndrome, Sickle cell anemia

Histiocytosis X, hemochromatosis, irradiation, Autoimmune destruction

Prolactin-sparing hypopituitarism

cause?

Hypothalamic disorders/interruption of the pituitary stalk => decreased anterior pituitary hormones*

*except prolactin –> lack of inhibition (dopamin)

Stimulants of GHRH and GH release

Stress, hypoglycemia, icreased [AA] (arginine)

Exercise, sleep (first 2 hrs)

oral clonidine

Test for GH hyposecretion

Insulin tolerance test–> hypoglycemia–>

GH> 20ng/mL (normal)

GH hypersecretion tests

IGF-1*–> no diurnal variation

–> consistently elevated in GH excess

*only for ages >5 yrs

Other:1.random blood sample–> markedly [GH]elevated

2.[GH]nml–> fails to supress w Glucose

Continuous stimulation of GnRH Rc => what is the effect?

inhibitory

eg GNRH agonists

young woman < 45 presenting with possible early menopause

FSH >40IU/L on 2 separate occasions > 4weeks apart

Dx?

Ovarian failure
Precursor molecule of ACTH

Pro-opio melanocortin –> translational cleavage =

ACTH + MSH + b – endorphin

Pt with hypernatremia

Low urine osmolarity

 

DDx

Diabetes insipidus

1.central–> inadequate ADH secretion

2.nephrogenic–> unresponsive renal tubules

Tests for Diabetes Insibidus

Overnight H2O deprivation test1 + ADH2(vasopressin)

Nm=1 [Osmol]urine increases, 2No effect

central DI = 1fail, 2[Osmol]urine increases

nephrogenic DI = 1,2 fail

relatively normovolemic Pt with hyponatremia

high [Na+]urine /[Osmol]urine

 

SIADH <–Lung-small cell ca, pancreatic adenoca, Intracranial tm,Interstitial lung disease,cerebral trauma,

Drugs: chlorpropamide

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