SECTION 2 — Overview of the Thyroid Gland

1⃣ What 3 hormones does the thyroid produce?

T3, T4, calcitonin

2⃣ What is T4 also called?

Thyroxine

3⃣ What is T3 also called?

Triiodothyronine

4⃣ What is the primary amino acid needed for T3/T4 synthesis?

Tyrosine

5⃣ What mineral is required to make T3/T4?

Iodine

6⃣ What protein stores T3/T4 in the thyroid?

Thyroglobulin

7⃣ What triggers thyroid hormone release?

TSH from anterior pituitary

8⃣ What controls TSH release?

TRH from hypothalamus

9⃣ What is the feedback loop for thyroid hormones?

Negative feedback

10⃣ What happens to TRH when T3/T4 rise?

TRH decreases

11⃣ What happens to TSH when T3/T4 fall?

TSH increases

12⃣ What is the most active form of thyroid hormone?

T3

13⃣ Which hormone has the longer half-life?

T4

14⃣ Where is T4 converted to T3?

Peripheral tissues

15⃣ What % of circulating thyroid hormone is protein-bound?

~99%

16⃣ What plasma proteins bind thyroid hormones?

Thyroxine-binding globulin, albumin, prealbumin

17⃣ What tissues are highly responsive to thyroid hormone?

Heart, skeletal muscle, liver, kidneys

18⃣ What tissues are less responsive?

Brain, spleen, gonads

19⃣ What is the role of thyroid hormone in metabolism?

Increases metabolic rate and oxygen consumption

20⃣ How does thyroid hormone affect heart rate?

Increases HR and cardiac output

21⃣ What happens to body temp under thyroid hormone?

Increases heat production

22⃣ How does thyroid hormone affect lipid metabolism?

Increases fat breakdown

23⃣ How does thyroid hormone affect carbohydrate metabolism?

Increases carb metabolism

24⃣ What is the effect on protein synthesis?

Enhances intracellular protein synthesis

25⃣ What happens to linear growth under normal thyroid function?

Promotes normal growth

26⃣ What happens to fetal brain development without thyroid hormone?

Severely impaired

27⃣ What happens to oxygen consumption?

Increases with thyroid hormone

28⃣ How does thyroid hormone affect reflexes?

Hyperreflexia in excess

29⃣ What happens to cholesterol in hypothyroidism?

Increases

30⃣ What happens to cholesterol in hyperthyroidism?

Decreases

31⃣ What is euthyroid?

Normal thyroid function

32⃣ What happens to TSH in primary hypothyroidism?

Increases

33⃣ What happens to TSH in hyperthyroidism?

Decreases

34⃣ What is the role of iodine in thyroid hormone?

Required to form T3/T4

35⃣ What happens to T3/T4 if iodine is deficient?

They decrease

36⃣ What happens to TSH if iodine is deficient?

It increases → goiter develops

37⃣ How are thyroid hormones metabolized?

In the liver

38⃣ How are thyroid hormones excreted?

In urine

39⃣ What happens to thyroid hormone half-life in hypothyroidism?

Prolonged

40⃣ What happens to half-life in hyperthyroidism?

Shortened

41⃣ What are symptoms of low thyroid hormone in infants?

Poor growth, intellectual delay

42⃣ What is congenital hypothyroidism?

Thyroid deficiency present at birth

43⃣ What is the storage mechanism for T3/T4?

Stored in inactive thyroglobulin

44⃣ What is the impact of low T3/T4 on metabolism?

Slows metabolism

45⃣ What is the impact of high T3/T4 on metabolism?

Speeds up metabolism

46⃣ What happens to cardiac workload under thyroid hormone?

Increases

47⃣ How does thyroid hormone affect ventilation?

Increases respiratory rate

48⃣ What is the primary regulatory hormone for thyroid?

TSH

49⃣ How often are thyroid hormone levels monitored during treatment?

Every 6–8 weeks initially

50⃣ What labs are most important to monitor?

TSH, T3, T4