Endocrinology Flashcards
What are the two endogenous chemicals that increase serum Ca2+ levels in the body?
1,25-(OH)2-DH
- Increases Ca2+ and PO4 absorption from the gut
- Increase Ca2+ resorption from bone
- Increases renal tubular Ca2+ and PO4 resorption
= primary ligand for vitamin D receptor in many tissues -> binds to vitamin D receptor in intestine, inducing expression of transport proteins
PTH
- Increases kidney Ca2+ resorption
- Decreases PO4 resorption
- Increases activity of kidney hydroxylase -> increased 1,25-(OH)2-D production
Main regulator of PTH release = serum Ca2+
What is the most common MODY type?
MODY3
MODY2, MODY3 and MODY5 make up for 90% all MODYs
What are the characteristics of MODY2, MODY3, MODY 5, MODY1?
MODY2
Second most common
Gene = glucokinase (mild decrease in beta-cell response to glucose)
Hyperglycaemia mild and non-progressive
MODY3
Most common
Gene = HNF-1 alhpa (hepatocyte nuclear factor)
Very sensitive to sulfonylureas
MODY5
Gene = HNF1-beta
Associated with: renal cysts/dysfunction, pancreatic exocrine dysfunction, hypospadias, joint laxity, uterine abnormalities
MODY1
Gene = HNF4-alpha
Very sensitive to sulfonylureas
Decreased levels of TAGs and apolipoprotein
Other than T1DM/T2DM, what are other rarer types of DM?
- Genetic defects of beta-cell function
- > MODY - Mitochondrial gene defects
- > Wolfram syndrome 1 (diabetes insipidus, DM, optic atrophy, deafness = DIDMOAD); Wolfram 2 (no diabetes insipidus)
- > avoid metformin (risk of severe lactic acidosis) - Neonatal diabetes mellitus
- > transient vs. permanent, IPEX (immunodysregulation, polyendocrinopathy and enteropathy, X-linked) - Genetic defects of insulin action (mutation in insulin receptor)
- > Donohue syndrome (IUGR, fasting hypoglycaemia, postprandial hyperglycaemia, profound insulin resistance), Rabson-Mendenhall syndrome (extreme insulin resistance, acanthosis nigricans, abnormalities teeth and nails, pineal hyperplasia), lipoatrophic diabetes, Stiff-Person (progressive stiffness, painful spasms of axial muscles), SLE
Does an ectopic posterior pituitary gland produce anterior or posterior problems?
Anterior
Failure of posterior pituitary to migrate and form the infundibulum causes anterior pituitary deficiencies
Normal stalk = isolated GH deficiency
Abnormal stalk = multiple pituitary hormone deficiencies
What are the side effects of GH therapy?
SCFE Pseudotumour cerebri Transient carbohydrate intolerance Transient hypothyroidism Scoliosis
Which is more specific for GH-deficiency: IGF-1 or IGF-BP3?
IGF-BP3
Vary less with age and nutrition -> more specific (though less sensitive) for GH action
IGF-1
Can vary greatly with age and nutritional status regardless of GH secreion -> sensitive, but not specific
What is the most common anterior pituitary tumour?
Prolactin-secreting tumours
MRI of sella = best diagnostic tool
What is the hormone that causes testicular enlargement?
FSH
What are the causes or high vs. low thyroxine-binding globulin? What is its significance?
Increased TPG -> increased total T4
Decreased TPG -> decreased total T4
This is because total T4 measures a combination of free T4 and bound T4
INCREASED TPG Oestrogen (OCP, pregnancy) Tamoxifen Narcotics Hepatitis, biliary cirrhosis
DECREASED TPG Androgens Glucocorticoids Nephrotic syndrome Inherited TPG deficiency
Does amiodarone cause hyper or hypothyroidism?
BOTH
Amiodarone is iodine-rich
-> also blocks peripheral deiodination of reverse T3 and T4 -> increased reverse T3 and T4, and decreased T3
HYPERthyroid = due to iodine
HYPOthyroid = too much iodine and peripheral deiodination
What type of hypothyroidism is not detected on the neonatal screening test?
SECONDARY hypothyroidism
Screening test does not detect low TSH levels (as seen in secondary hypothyroidism)
When administering thyroxine to neonates/infants with hypothyroidism, what do you NOT mix it with?
Do NOT mix thyroxine with: (as can be bound)
Soy protein formula
Iron
Calcium supplements
What change does alkalosis cause to calcium levels?
HYPOcalcaemia
As pH increases, albumin becomes more ionised into anions -> causes free calcium to bind more strongly with albumin
What are the counter-regulatory hormones?
= Hormones that counter the effect of insulin
Glucagon
Adrenaline
Cortisol
Growth hormone