Endo - 1-21 - Hypothyroidism

Front 1

Is hypothyroidism a dx or clinical syndrome?

Back 1

clinical syndrome

Front 2

Most common type of hypothyroidism

Back 2

Primary

Front 3

Types of hypothyroidism that can occur

Back 3

Primary
Secondary - Pit or hypothal
Resistance to thyroid hormone - usually to a gene coding for nuclear thyroid hormone receptors. Can cause signs of hypo and hyperthyroid.

Front 4

More common in men or women?>

Back 4

women

Front 5

Congenital hypothyroidism

Back 5

Agenesis of the gland.

Front 6

Quebec score

Back 6

Scores clinical features of infants

>=4 is predictive of hypothyroidism, and avg score of hypothyroid pts is 8.6

Front 7

Why is tx of cnogenital hypothyroidism so important?

Back 7

If you treat within the first three months, you severely reduce the chance of them having a low IQ.

Front 8

Cretinism

Back 8

Combined maternal and fetal iodine deficiency leading to a type of congenital hypothyroidism.

Results of treating these infants are less beneficial than treating congenital hypothyroidism where there is agenesis of the gland.

Front 9

Three classes of thyroid hormone effects

Back 9

In hypothyroidism, you see....

Developmental delay --> cognitive dysfunction

Slow metabolism

Reduced expression of beta-adrenergic receptors. (most important in muscle)

Front 10

Other sx of hypothyroidism

Back 10

Dry skin
Cold intol
Fatigue
Puffy hands and face
constipation
weight gain
tingling of fingers and carpal tunnel
bradycardia
heavy menses
slowed reflex relaxation
Galactorrhea due to TRH-stimulated prolactin production

Front 11

Levels of CPK, LDL, hyalouronic acid, cortisol in pts with hypothyroidism

Back 11

CPK - Increased
LDL - increased
Hyaluronic acid - increased (leading to myxedema)
Cortisol - decreased levels

Front 12

Levels of digoxin and anesthetics in pts with hypothyroidism

Back 12

Clear them both slower.

Front 13

DDx of primary hypothyroidism

Back 13

Iodine deficiency - Most common in world
Hashimoto's thyroiditis - most common in West
Congenital hypothyroidism - thyroid agenesis
Thyroiditis - Often resolves spontaneously.
Drugs - e.g. amiodarone or lithium. Or PTU or methimazole
Surgical or radioiodine ablation.

Front 14

DDx of secondary hypothyroidism

Back 14

Hypothalamic disease - e.g. tumor (craniopharyngioma), infiltrative disorder, trauma, surgery, radiation
Pituitary disease
Genetic - e.g. TSH deficiency

Front 15

DDx of resistance to thyroid hormone

Back 15

Genetic mutations - usually affects the beta-1 subtype of the nuclear thyroid hormone receptor gene.

Front 16

Therapy of hypothyroidism

Back 16

Endemic goiter - Supplying iodine

Other forms - thyroxine

Front 17

How to measure dose in tx of hypothyroidism

Back 17

Measuring TSH level (not until 6 weeks because you have to wait for 6 half-lives of levothyroxine to get steady state)

Front 18

Is TSH level useful to monitor dose in a pt with secondary hypothyroidism?

Back 18

no - use clinical status and free T4

Front 19

Pregnancy tx of hypothyroidism

Back 19

Inc catabolism of thyroxine so dose should be increased

Front 20

Coexisting heart disease - tx of hypothyroidism

Back 20

Lower starting dose of thyroxine.

Front 21

Hypoadrenalism - tx of hypothyroidism

Back 21

treat this before init of thyroxine therapy. You don't wanna precipitate an adrenal crisis.

Front 22

Overtreatment with thyroxine

Back 22

can cause afib and hasten bone loss.

Front 23

Subclinical hypothyroidism

Back 23

Can represent the early stage of thyroid gland failure.

Front 24

Myxedema coma

Back 24

Results from prolonged and marked def of thyroid hormone.

Manifests with myxedema, hypothermia and loss of consciousness.

A medical emergency

Note - the myxedema is just a generalized pitting, puffy, edema. It is not a rash (pretibial myxedema)

Front 25

How to disting btwn primary and sec hypothy

Back 25

TSH and T4 levels.

TSH high in primary and not high in secondary.

High in receptor resistance too. And T4 is high in receptor resistance.

Front 26

Why isn't TSH low in pts with secondary hypothyroidism?

Back 26

It isn't glycosylated. So it shows up in the assay,but it isn't actually useful.

Front 27

Characteristic of TSH in hypothalamic/pituitary disease

Back 27

it often has reduced bioactivity - not glycosylated.

Front 28

Incidence of hashimotos increases with...

Back 28

age

Front 29

Tongue in pts with hypothyroidism

Back 29

can be very large

Front 30

Pit-1 and prop-1 mutations

Back 30

can cause a genetic cause of secondary hyperthyroidism

Front 31

Question:
A patient was started on thyroxine therapy for primary hypothyroidism 7 days ago.
He calls your office and suggests that his TSH be checked now to determine whether
the prescribed dose is adequate. Is this a good idea? Why?

Back 31

no, steady state takes 6 weeks to reach.

Front 32

How might initiation of thyroid hormone replacement therapy in a hypothyroid
patient aggravate underlying myocardial ischemia?

Back 32

You will inc O2 reqiurement bc of mitochondrial effect and you will be increasing HR.
So you must be very careful here.
Thyroid hormone will inc HR, diminish periph resistance, and will increase myocardial
efficiency eventually. But the mitochondrial effect can mess things up short term.

So you should address coronary artery stenoses quickly.

Front 33

Hypothyroidism effect on mitochondria

Back 33

Less mitochondria - so burning less energy at rest