6a. Endocrine Health - Thyroid Flashcards
What is TRH?
Thyrotropin releasing hormone
What does TRH do?
Stimulates TSH release from the anterior pituitary gland
What does TSH do?
Stimulates thyroid hormone production from the thyroid gland - T4 and T3
Activates iodide uptake via the Na/iodide symporter (SIS)
What percentage of thyroid hormone is T4?
90%
What is the alternative name for T4?
Thyroxine
Which of T4 and T3 is the strongest, more active hormone?
T3 - 4x the strength of T4
What does T3 do?
Increases growth
Bone development
CNS development
Increases BMR/HR
Activates metabolism
What does RT3 do?
Protects tissues from excess thyroid hormones
Biologically inactive - puts the handbrake on T3
What are iodothyronine deiodinases?
Selenoproteins that regulate thyroid hormone homeostasis
What does deiodinase 1 and 2 do (D1/D2)?
Convert T4 to T3
What does deiodinase 3 do (D3)?
Converts T4 to RT3
What does thyroid peroxidase (TPO) do?
Enzyme that helps produce T4 and T3
(catalyses iodination of tyrosine residues in thyroglobulin)
Which nutrients are needed to make TPO?
Tyrosine
Iodine
Iron
Which minerals are needed as co-factors in the synthesis of enzymes and thyroid hormones?
Se
Zn
Cu
Which vitamins are needed to support thyroid hormone synthesis and function?
ACE
B2, B3, B6, B12
What is the role of vit D in thyroid synthesis?
Immune modulation in AI thyroid disorders and VDR polymorphism
Examples of iodine rich foods
Sea veg
Ocean fish
Shellfish
Eggs
Dairy
What is the cause of iodine deficiency?
Dietary deficiency
Who is more at risk of iodine deficiency?
Low/no fish or dairy in diet
Pregnant women
Vegans
Why can high goitrogen foods cause thyroid disorders?
Goitrins, thiocyanates and nitriles in the foods reduce iodine uptake and have anti-TPO activity
Examples of goitrogen foods
Raw brassicas
Soya (fermented ok)
Millet
Peanuts
Pine nuts
How can people consume excess iodine?
Over-iodised salt
Animal milk rich in fortified iodine
Iodine-containing supplements
Radiocontrast dyes
Some medications
What is the Wolff-Chaikoff effect?
Helps reject excess iodine
What can inhibited Wolff-Chaikoff effect lead to?
Subclinical or clinical hypothyroidism
Where is T4 converted to T3 or RT3?
Liver
Kidneys
How are the thyroid hormones metabolised?
Deiodination
Sulphation
Glucuronidation
Which thyroid hormone decreases if RT3 increases?
T3
In which situations does an increase in T4 to RT3 occur?
Chronic illness - to low metabolism
High stress
Zn/Se/Fe deficiency
Fasting/significant calorie restriction
Advancing age
Which thyroid pathology does increased RT3 present as?
Hypothyroidism
What do HPT disrupters interfere with?
HPT axis
Thyroid hormone synthesis, secretion, transportation, metabolism and function
Examples of HPT disrupters
Fluoride
Chlorine
Pesticides
BPAs
Phthalates
Bromine
Glyphosate
Ways to avoid HPT disrupters
Drink filtered water
Fluoride free toothpaste
Eat organic
Avoid farmed fish/processed foods
Limit time in chlorinated pools
Avoid plastic packaging
Examples of medications that exert effects on thyroid function
Dopamine/glucocorticoids - decrease TSH secretion
Beta blockers - reduce T4 to T3
Diuretics/NSAIDs - reduce T4 to T3 binding
Oestrogen - increase thyroglobulin
Why does gut dysbiosis negatively effect thyroid function?
Microbes regulate iodine uptake and degradation
What intestinal imbalances are common in AITD?
Low SCFA production
Elevated zonulin (intestinal permeability)
Elevated serum LPS (chronic low grade inflammation)
Optimal range of TSH in testing
0.4 - 2.5
Optimal range of total T4 in testing
70 - 150
Optimal range of free T4 in testing
12.8 - 19.5 pg/ml
Optimal range of free T3 in testing
3.2 - 4.5
Optimal range of RT3 in testing
11 - 18 ng/dl
How is subclinical hypothyroidism interpreted in testing?
High TSH
Normal T4
Normal T3
How is hypothyroidism interpreted in testing?
High TSH
Low T4
Low T3
How is subclinical hyperthyroidism interpreted in testing?
Low TSH
Normal T4
Normal T3
How is hyperthyroidism interpreted in testing?
Low TSH
High T4
High T3
How is secondary hypothyroidism interpreted in testing?
Low TSH
Low T4
Low T3
What is the best test for testing iodine status?
Urine iodine test
What should iodine levels be in children/adults?
100-199 mcg/L
What should iodine levels be in pregnancy?
150-249 mcg/L
What iodine level is considered as insufficiency?
<100 mcg/L
What iodine level is considered as severe deficiency?
<20 mcg/L
What signs of hypothyroidism can be seen during a physical exam?
Goitre
Dry skin
Nail beading
Thinning eyebrows
Hair loss
Low BP
Bradycardia (<60 BPM)
Which SNPs on a thyroid report may suggest a thyroid imbalance?
HLA - AI
TNF - inflammation
SLCO1B - transport of hormones into cells
VDR - vit D as a co-factor
BCO1 - retinol as a co-factor
SULT/UGT - detoxification
What is primary hypothyroidism?
Pathology is occurring within the thyroid gland
TSH is high due to low T4/T3
What is secondary hypothyroidism?
Pathology is occurring within the pituitary gland
Low TSH to signal to thyroid gland to release T4/T3
What is tertiary hypothyroidism?
Inadequate TRH
What is peripheral hypothyroidism?
Insensitivity to thyroid hormones
What is subclinical hypothyroidism?
Slightly high TSH and normal T4/T3
General signs/symptoms of hypothyroidism
Fatigue
Weight gain
Puffy face
Intolerance to cold
Joint/muscle pain/weakness
Dry skin
Hair loss/thinning
Constipation
Fertility problems
Goitre
Bradycardia
Risk factors/causes of hypothyroidism
Iodine deficiency/excess
Women
Age
Lack of nutrients - Fe, Se, Tyrosine, Zn, D, C, Cu, B2/3/6/12
Chronic stress - inhibits TSH release
Infection/inflammation
Alcohol
Smoking
Drug induced - amiodarone/lithium
What is Hashimoto’s thyroiditis?
AI disease
Attacks thyroid tissue causing reduced thyroid hormones
What is the ratio of women:men of getting Hashimoto’s?
10:1
What are the testing markers for Hashimoto’s?
High TSH
Low T4
Increased anti-thyroid peroxidase (TPO) antibodies
Which two infections are implicated in Hashimoto’s?
EBV
H. pylori
(as triggers for the AI)
What are the risk factors/causes of Hashimoto’s?
Excess iodine
Coeliac disease
Genetic polymorphisms - VDR, MTHFR
Heavy metals
Triclosan - found in personal care products
What is the allopathic treatment for Hashimoto’s?
Levothyroxine (synthetic T4)
When is it best to take levothyroxine?
Empty stomach in the morning
Take food/other drinks at least 1hr after
What can affect the absorption of levothyroxine?
Coeliac disease
Coffee
PPIs
Common triggers and mediators in the development of thyroid disorders
Iodine status
Micronutrient insufficiencies
Intestinal permeability
Inflammation
Food sensitivities
Goitrogens
HPA axis imbalance (stress)
SNPs
Medications
Environmental toxins
Radiation
Surgery
Naturopathic approach to hypothyroidism
Address micronutrient status
Review iodine status
Optimise digestion
Support methylation
Remove thyroid disruptors
Address possible dysbiosis
Increase SCFA producers
Address stress
Support detoxification/elimination
Avoid heavy metals
Assess for coeliac disease
Identify food intolerances
Increase exercise
Reduce inflammation
Blood sugar balance
Reduce goitrogenic compounds
Address intestinal permeability
Why is Zn needed for thyroid support?
Co-factor for D2
TRH synthesis
How could Zn deficiency be indicated on a test?
Low T3
High RT3
Supplement dosage for Zn in thyroid support
15-30 mg/day
Why is Fe needed for thyroid support?
TPO is a haem-containing enzyme needed in initial steps of hormone synthesis
Deficiency decreases T4 and T3
Supplement dosage for Fe in thyroid support
10mg - maintenance
30mg - deficient
(test before)
Why is iodine needed for thyroid support?
Modulates thyroid response to TSH
Supplement dosage for iodine in thyroid support
150-400mg/day
Why is Se needed for thyroid support?
AO
Anti-inflammatory
Increases T3
Supplement dosage for Se in thyroid support
150-200mg/day
Why is tyrosine needed for thyroid support?
Thyroglobulin precursor
Supplement dosage for tyrosine in thyroid support
200-500mg/day
Why is vit A needed for thyroid support?
Modulates thyroid hormone receptor function
What can insufficiency in vit A cause?
Increases TSH
Reduces iodine uptake in thyroid
What can cause vit A insufficiency?
Low intake
BCO1 SNP
Supplement dosage for vit A for thyroid support
2000 iu/day
What role does vit D have in thyroid support?
Immune-modulatory
Supplement dosage for vit D for thyroid support
2000 iu/day
Herbal approaches to hypothyrodism
Nigella sativa (1g/day) - reduces TSH/TPO
Thyroid glandulars - provides T4/3, relevant AAs and micronutrients
Ashwagandha - improves TSH/T4/T3 levels
Guggul - enhances iodine uptake
What is hyperthyroidism?
Increased levels of thyroid hormones
What are the two sub-divisions of hyperthyroidism?
Thyrotoxicosis
Thyroiditis
What is thyrotoxicosis?
Increased synthesis of thyroid hormones
What is the key cause of thyrotoxicosis?
Grave’s disease (80%)
What is thyroiditis?
Increased release of stored thyroid hormones due to thyroid damage
What are the key causes of thyroiditis?
Viral infections
AI
Who is more affected by hyperthyroidism?
Women (10:1)
Key signs/symptoms of hyperthyroidism
Weight loss
Thirst
Diarrhoea
Tachycardia
Palpitations
SOB
Goitre
Irritability
Nervousness
Anxiety
Insomnia
Warm, moist skin
Sweating
Heat intolerance
What is Grave’s disease?
AI hyperthyroidism
What two antibodies are present in Grave’s disease?
TRAbs
TPO
Characteristic signs/symptoms of Grave’s disease
Red, swollen eyes
Eyelid retraction
Eyeball protrusion
Excess eye watering
Double vision
Painless rash - lower legs/top of feet
Causes/risk factors for hyperthyroidism
Family history
Stress
Inflammation
Excess iodine intake
Dysbiosis
Food allergy/intolerance
Heavy metals
Smoking
Infections
Vit D/Se/CoQ10 deficiency
What FT3/FT4 ratio distinguishes Grave’s from thyroiditis?
> 0.3
What markers will be present in thyroiditis?
Raised CRP and ESR
Natural approach to support hyperthyroidism
AO - ACE, Se, Zn, D
Energy - B vits, carnitine, Mg, CoQ10
Glutathione support
Avoid iodine
Increase goitrogens
Reduce inflammation (increase O3 but not via fish)
Quercetin
Support blood sugar balance
Support stress/HPA axis
Address gut health
Support sulphation
Support glucuronidation
Increase calorie intake - nuts/seeds/avocado/olives/protein rich
Why is carnitine important in hyperthyroidism?
Antagonises thyroid hormones inhibiting T4/T3
Prevents/reverses muscle weakness
Supplement dosage of carnitine to support hyperthyroidism
2000-4000mg/day
Why is vit D important in hyperthyroidism?
Immune modulator
May slow disease progression
Herbal approaches to hyperthyroidism
Passionflower/valerian - nervines - reduce stress
Ashwagandha
Mg/theanine - reduce anxiety
Lemon balm - blocks thyroid hormone activity