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Basic Science II > Endocrine (Altose): Thyroid and Parathyroid Hormones > Flashcards

Endocrine (Altose): Thyroid and Parathyroid Hormones Flashcards

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1
Q

What is the hormonal pathway leading up to the release of thyroid hormones?

A

TRH (hypothalamus) –> TSH (anterior pituitary) –> T3/T4 bind to TBG (thyroid) –> TBG carries T3/T4 throughout the bloodstream

TRH: Thyroid Releashing Hormone

TSH: Thyroid Stimulating Hormone

TBG: thyroxine binding globulin

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2
Q

What is the first line screening test for thyroid dysfunction?

Why is this useful?

What values indicate hyper-, eu-, and hypo-thyroid states?

A

TSH levels

Iodine and T3/T4 (thyroid hormones) inhibit TRH and TSH secretion, so the level of TSH is a reflection of circulating T3/T4

~0-3: hyperthyroid

~3-10: euthyroid

~10-15: hypothyroid

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3
Q

What is the primary negative feedback loop involved in thyroid hormone regulation?

A

TRH and TSH stimulate thyroid hormone secretion

Iodine and thyroid hormone inhibit TRH and TSH secretion

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4
Q

Why are T4 levels a poor indicator of thyroid function?

A

T4 levels are not reliable due to extensive protein binding to TBG.

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5
Q

80% of T3 is produced by this process…

A

Extra-thyroidal de-iodination of T4

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6
Q

Compared to T4, T3 is ___ potent and _____ protein bound.

A

More, less

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7
Q

How much T3/T4 is free circulating hormone?

A

<0.1% of the T3 and T4 produced by the body.

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8
Q

What are some symptoms of hyperthyroidism?

A

Anxiety

Wt loss

Diarrhea

Weakness

Tremors

Warmth

Heat intolerance

Tachycardia

Increased pulse pressure

HF

AFib

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9
Q

What are some intrinsic causes of hyperthyroidism?

A

Goiters

Adenoma

Graves

Thyroiditis

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10
Q

What are some extrathyroid causes of hyperthyroidism?

A

Iatrogenic injury

Excess iodine

Hypothalamic tumor

Carcinoma

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11
Q

How should hyperthyroid patients be optimized?

A

They should be euthyroid on DOS.

This can take 6-8 weeks (NaI/KI –> PTU, methimazole)

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12
Q

In hyperthyroid pts, what meds should you avoid?

A

Sympathetic system stimulating meds (ketamine, pancuronium/pavulon, ephedrine, halothane)

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13
Q

Hyperthyroidism is commonly accompanied by this autoimmune disease. What is the disease and how does it effect our anesthetic plan?

A

Myesthenia Gravis

We need to reduce our initial NMB dose.

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14
Q

Thyroidectomies are common surgeries that hyperthyroid patients undergo.

What are some common post-op complications of thyroidectomies?

A

Superior and Recurrent Laryngeal Nerve damage

Hematoma

HypoPTH (leads to hypo Ca++) w/ stridor

Corneal injury (due to exophthalmos of Graves)

Stridor can last 24-96 hours post-op

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15
Q

What are risk factors for the occurrence of thyroid storm? (Think Sx situations and disease states)

A

Thyroid Storm Is Deadly Man:

Trauma

Surgery

Infection

DKA

Mental status changes

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16
Q

What diseases/intra-op malignancies do thyroid storms resemble?

A

Malignant Hyperthermia

Pheochromocytoma

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17
Q

What are intra-operative treatments for thyroid storm?

A

Beta-blockade (esp with propranolol which inhibits T4->T3 conversion)

Decadron (reduces thyroid secretion and inhibits T4->T3 conversion)

PTU/methimaxole (via NGT)

NaI/KI

IVF

Cooling

Ofirmev

18
Q

What are absolutely contraindicated in the treatment of thyroid storm?

A

Any drugs that increase sympathetic output or hyperthermia

Aspirin! (can increase T3/T4 levels)

19
Q

What are symptoms of hypothyroidism?

A

Depression

Lethargy

Cold intolerance

Decreased response to hypoxia/hypercapnia

Bradycardia

20
Q

What are primary and secondary causes of hypothyroidism?

A

Primary:

Autoimmune diseases

Iatrogenic injury

Thyroiditis

Iodine Deficiency

Secondary:

Pituitary dysfunction

Hypothalamic dysfunction

21
Q

What are the effects of decreased thyroid function on MAC?

A

None

22
Q

What are some pre-op and intra-op concerns with hypothyroidism?

A

No real pre-op concern; pt does not have to be euthyroid unless severe

Watch out for bradycardia, etc.. ; no agents absolutely contraindicated

Consider A-line to manage CV

23
Q

What is myxedema coma?

What is its mortality rate?

When does it occur?

What are its symptoms?

How do we treat it?

A

An outcome of severe hypothyroidism with a mortality rate of 25-50%

Usually occurs after stressful events (MI, infection drugs)

Symptoms: Stupor, hypoventilation, HoTN, hyponatremia

Treatment: IV thyroid replacement, steroids, warming

24
Q

~50% of your body’s serum Ca++ is bound to this protein. What is it?

What is the rest bound to?

A

Albumin

The other 45% are ionized free (bound to nothing)

25
Q

What are the functions of PTH (parathyroid hormone)?

A

Maintain serum Ca and Mg (renal reabsorption, bone resorption as well as GI absorption which requires vit D)

Phosphate excretion (occurs renally as Ca++ is reabsorbed)

Note: Mg+ will tend to follow Ca++

26
Q

What is Calcitonin?

Where does it come from?

What does it do?

A

It is a hormone secreted from the thyroid gland?

It inhibits PTH (wastes Ca/Mg, save phosphate)

27
Q

Vitamin __ assists Ca++ absorption from the ______________.

A

D, GI tract

28
Q

HyperPTH means a high level of this ion.

A

Ca++

29
Q

What are some primary causes of hyperPTH?

A

Hyperplasia (too much cell growth)

MEN (multiple endocrine neoplasia) syndrome

Ectopic production (tumor)

Adenoma

30
Q

What are some secondary causes of hyperPTH?

A

Hypocalcemia

Hyperphosphatemia

31
Q

What are symptoms of hyperPTH?

A

Stones Bones Groans Moans:

kidney Stones (nephrolithiasis)

Bone pain

GI problems (ulcers)

Psychiatric overtones (fatigue, depression, thirst)

CV symptoms:

bradycardia, HTN, short QT, heart block

32
Q

What are some treatments for HyperCa++?

A

IVF + Lasix

Calcitonin

Dialysis

Biphosphonates

33
Q

What population of patients are especially susceptible to the negative effects of hyperPTH and should be surgically treated?

A

Pregnant women due to high maternal/fetal mortality

34
Q

Unlike many other electrolytes, excessive amounts of calcium tend to be excitatory/depressive. (choose one)

A

Depressive

35
Q

What are some post-op complications associated with parathryoidectomies?

A

Airway edema

Nerve injury

Electrolyte imbalance (Ca/Mg/Phos)

Hungry bone syndrome (bones absorb Ca++ at high rates in response to surgery)

36
Q

What are some causes of hypoparathyroidism?

What electrolyte imbalance does it cause?

A

Causes:

Removal of PTH glands

Neck trauma

Severe hypoMg (Ca++ and Mg+ follow each other)

Malignancies

Causes HypoCa++

37
Q

What are some signs of HypoCa++?

A

Spasms

Seizures

Latent tetany (Trousseau)

Parasthesias

Fatigue

Stridor

CHF

HoTN

Long QT

38
Q

Bonus. What is another name for Versed?

A

Midazolam. Good job, you’re awesome.

39
Q

Most common cause of hyperthyroidism is..

A

Graves disease

40
Q

How do you distinguish between thyroid storm and MH?

A

Hyperventilation of pt will not decrease PaCO2 in MH but will decrease in thyroid storm.

(Gauge through ABGs)

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