Thyroid

Question 1

Formation of thyroid hormones

Answer 1

Iodide I- is pumped into the follicle 
Iodide oxidised to iodine I2
Forms with tyrosine to form 
-DIT
Or.. MIT 
These are attached to thyroglobulin 
They bind to make either 
T3- DIT + MIT
T4- DIT + DIT 

These thyroid hormones are stored in the thyroid colloid until needed

Question 2

Stimulation of thyroid hormone release

Answer 2

TRH (thyrotropin releasing hormone) enters hypophoyspheal portal artery to the anterior pituitary
Stimulates release of TSH (thyroid stimulating hormone) from the ant pituitary
T3 and T4 unbind from the thyroglobulin and enter the blood stream
They are attached to thyroid binding globulin

Question 3

Negative feedback loop of thyroid hormones

Answer 3

T3 and T4 negatively feed back to the pituitary and hypothalamus if levels get too high

Question 4

Metabolic effects of thyroid hormone

Answer 4

↑ O2 consumption leading to ↑ heat production as a result of ↑ metabolism
↑ glucose uptake in GI tract, ↑ gluconeogenesis, ↑ glycolysis
↑ fat breakdown and ↓ lipids circulating in blood
↑ protein breakdown and synthesis

Question 5

Systemic effects of thyroid hormone

Answer 5

↑ heartrate and cardiac output
↑ digestion, appetite and absorbtion
↑ breathing rate
↑ alertness

Question 6

Developmental effects of thyroid hormone

Answer 6

↑ growth

Normal brain development

Question 7

Normal micro anatomy of a follicle in thyroid

Answer 7

Calcitonin releasing C cells
Cuboidal epithelium
Colloid

Question 8

How Thyroid hormones ↑ metabolism

Answer 8

T3 + T4 easily pass cell membrane 
T4 converted to T3 
T3 attaches to receptor sites 
Causes a change in DNA transcription, ↑ protein synthesis 
Protein= enzymes which ↑ metabolism

Question 9

How does thyroid hormone ↑ metabolism

Answer 9

Binds to receptor site
Stimulates DNA transcription 
↑ in mitochondria 
↑ synthesis of ATP
= more energy and ↑ metabolism

Question 10

Thyroid Stimulating Hormone effect on the thyroid

Answer 10

↑ iodide trapping 
↑ number and size of follicles 
Synthesis of more thyroglobulin 
↑ synthesis of T3 + T4
↑ blood flow to the thyroid gland

Question 11

Hypothyroidism causes

Answer 11

Primary - problem with thyroid gland

Secondary- problem with pituitary
- thyroid atrophy

Tertiary- problem with hypothalamus

Question 12

Primary Hypothyroidism Causes

Answer 12

Autoimmune destruction of thyroid gland cells
Iodine deficiency
Deficiency of thyroid enzymes
Destruction or removal

Question 13

Signs of Hypothyroidism

Answer 13

Eyes wide apart 
Receding hairline
Flat nose and pasty skin 
Small size
Brain development
GOITRE

Question 14

Hyperthyroidism Causes

Answer 14

1. Graves’ disease
2. Thyroid adenoma
3. TSH secreting adenoma

Question 15

Graves’ disease

Answer 15

Caused by autoimmune antigen stimulating TSH receptors
Release of T3 and T4
No negative feedback to pituitary as TSH not secreted for negative feedback
= hyperthyroidism

Question 16

Graves’ disease signs

Answer 16

Goitre
Bulging eyes due to deposition of fluid
Warm moist skin
Tachycardia