FR Review 2 - Thyroid, DM, and Weight Loss

Question 1

What are the 2 thyroid hormones and what is their relationship?

Answer 1

L-thyroxine (T4) and Liothyronine (T3). T4 is the precursor to T3 which is the active hormone.

Question 2

Describe the hypothalamic-pituitary-thyroid axis.

Answer 2

Hypot releases TRH –> AP releases TSH –> thyroid releases T4 –> T4 deiodinated to T3 in periphery.

Question 3

How is the majority of T3 and T4 present in the blood?

Answer 3

Bound to plasma protein (inactive) –> thyroxine binding globulin (TBG)

Question 4

What increases and decreases TBG?

Answer 4

Inc: pregnancy and oral contraceptives
Dec: anabolic steroids (T inc metabolic requirements which increases need for free T3)

Question 5

State and describe the drug most used to treat hypothyroid.

Answer 5

Levothyroxine (T4, aka Synthroid) –> slow on and slow off. Max effect of one dose reached in 10 days.

Question 6

What lab value indicates hypothyroidism (cretinism)?

Answer 6

High TSH, low T3 and T4

Question 7

What is the dosing regimen for hypothyroidism?

Answer 7

50-100 mcg synthroid qd titrated up to normal TSH

Question 8

In dosing synthroid what considerations are given to pregnant females and to cardiac patients?

Answer 8

pregnant: need higher dose (TBG increases)
cardiac: need lower dose (don’t overstimulate heart)

Question 9

Why is synthroid taken on an empty stomach?

Answer 9

Synthroid sticks to food, dec absorption

Question 10

T/F: Hyperthyroid disease is much easier to treat than hypothyroid disease.

Answer 10

False –> hypothyroid easy to manage by titrating Synthroid. Hyperthyroid often involves surgical removal of the thyroid gland.

Question 11

What is the mechanism of action of methimazole?

Answer 11

Blocks formation of thyroid hormones by inhibiting oxidation of dietary iodine. Does not block conversion ot T4 to T3.

Question 12

What is the mechanism of action of propylthiouracil (PTU) and why are its effects delayed?

Answer 12

Inhibits oxidation of thyroid hormone. Max effects not seen until all previously formed T4/T3 is exhausted.

Question 13

Why is a high dose of PTU the treatment of choice in thyroid storm?

Answer 13

PTU blocks peripheral conversion of T4 to T3

Question 14

Other than PTU, what 2 medications are the ideal treatment of thyroid storm?

Answer 14

IV or PO propranolol –> non-selective beta blocker

High dose dexmethasone –> inhibit T4 - T3 conversion (monitor BGL in Pt’s on dexmethasone)

Question 15

When in pregnancy is PTU preferred over methimazole?

Answer 15

During the 1st trimester –>PTU still crosses blood-placenta barrier and may enter breast milk.

Question 16

Does iodine cause hypothyroidism or hyperthyroidism?

Answer 16

Can cause either

Question 17

What is the purpose of giving radioactive iodine?

Answer 17

Iodine goes straight to the thyroid, taking the radiation with it to destroy thyroid tissue. This is used to treat hyperthyroidism.

Question 18

Differentiate TID from T2D.

Answer 18

T!D: inability to produce insulin
T2D: Down regulation of insulin receptors and desensitization of insulin receptors s/p poor diet, lack of exercise, and obesity.

Question 19

What is the general rule for dosing insulin and where do you start for a new patient?

Answer 19

1 unit of insulin used per kg of body weight. Start a new patient at 80% of daily use then titrate PRN.

Question 20

What is the main drug that induces hyperglycemia? List some others that cause hyperglycemia.

Answer 20

1 - steroids. Others - glucagon, epi, thyroid hormones, oral contraceptives, HCTZ/diuretics (mild increase)

Question 21

List and describe the insulins in each category of formulation.

Answer 21

Immediate: Lispro - closest to regular insulin
Short: regular insulin - quick on, quick off
Intermediate: NPH - administered BID
Long: Detemir and Glargine - administered QD

Question 22

Describe the initial insulin dosing regimen for a new T1D patient.

Answer 22

Start with conventional insulin BID - 2/3 dose in the morning and 1/3 at bedtime - with q6h BGL checks

Question 23

What does it mean for insulin to be “70/30”?

Answer 23

70% long acting agent (NPH) and 30% short acting agent (Lispro) in one vial. The first number is always indicative of the longer acting insulin’s percentage

Question 24

Why is an insulin syringe rolled rather than shaken to mix the suspension?

Answer 24

Shaking denatures the proteins causing foam formation.

Question 25

What effect does beta blocker use have on DM patients?

Answer 25

Beta blockers mask the S/S of hypoglycemia

Question 26

What is the mechanism of action of sulfonylureas?

Answer 26

Block K channels on beta cells causing an increased release of stored insulin. The drugs also cause hepatic, adipose, and muscle cells to take in more insulin.

Question 27

List some examples of sulfonylureas.

Answer 27

Glimepride, Glipizide, Glyburide.

Question 28

What is the mechanism of action of biguanides and what must be present for them to be effective?

Answer 28

They reduce hepatic glucose production. Only effective in the presence of insulin.

Question 29

List examples of biguanides.

Answer 29

Metformin and phenformin (pulled from market s/p risk of metabolic acidosis).

Question 30

What is the formula to determine creatinine clearance in males and in females?

Answer 30

CrCl = [(140 - age) * weight in kg] / [72 * serum creat.]

In females multiply answer by 0.8

Question 31

What is the mechanism of action of thiazolidineediones?

Answer 31

reduce peripheral insulin resistance. (not hot)

Question 32

What is the mechanism of action of Meglitinides?

Answer 32

Short acting secretagogues (increase insulin secretion) that act similar to sulfonylureas.

Question 33

List 2 examples of meglitinides.

Answer 33

Repaglinide and Nateglinide

Question 34

What is the mechanism of action of Exenatide?

Answer 34

Functional analogue of GLP-1 –> increases insulin secretion and delays gastric emptying (inc satiety).

Question 35

What is the mechanism of action of acarbose and miglitol?

Answer 35

alpha-glucosidase inhibitor reducing the digestion of complex carbohydrates in the gut.

Question 36

What is the mechanism of action of pramlinitide?

Answer 36

Synthetic amylin analogue with longer 1/2 life - works like a GLP-1 agonist (inc insulin secretion and delays gastric emptying)

Question 37

What is the mechanism of action of canaglifozin?

Answer 37

SGPT-2 inhibitor. SGPT-2 is an enzyme in the kidney that promotes reabsorption of GLC. If reabsorption of GLC is inhibited, more GLC stays in the urine and BGL decreases.

Question 38

What is the treatment of DKA?

Answer 38

Insulin gtt at 0.5-10 u/hr to decrease BGL by 100 per hour. Also admin phosphate and potassium.

Question 39

What is the mechanism of action of Orlistat?

Answer 39

Binds to and inhibits pancreatic lipase preventing the absorption of about 30% of dietary fat. Satiety inc.

Question 40

What is the mechanism of action of Phentermine?

Answer 40

Sympathomimetic that acts as an appetite suppressant. Similar to methamphetamine.

Question 41

What is the mechanism of action of Liraglutide?

Answer 41

GLP-1 agonist increases insulin secretion and delays gastric emptying promoting satiety.

Question 42

What is the mechanism of action of Qsymia?

Answer 42

A combination of a sympathomimetic and an antiepileptic that is known to cause weight loss.

Question 43

What is the mechanism of action of Contrave?

Answer 43

Combination (buproprion and naltrexone) of an atypical antidepressant that blocks dopamine (reward NT) and a long acting narcotic receptor antagonist that causes weight loss. Combo of drugs synergistically blunt the reward mechanism in the brain.