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Case 9: Thyroid/Mental health - Coggle Diagram
Case 9: Thyroid/Mental health
Anatomy and Physiology of the Thyroid gland
Anatomy
Gland itself
Ductless gland
There are thyroid and parathyroid glands
Parathyroid glands
Produce parathyroid hormone when low blood Ca2+
Found in anterior aspect of the neck, wraps arnd trachea
Blood and nerve supply
Blood supply
Blood supplied from superior thyroid artery (branch of external carotid), and inferior thyroid artery (branch of thyrocevical trunk, from subclavian artery)
Blood drained into superior, inferior, and middle thyroid veins
Nerve supply
Sympathetic fibres from superior, middle, and inferior cervical ganglia
PSNS fibres from superior and recurrent laryngeal nerves (branches of vagus nerves)
Lymph nodes
Drain into:
Histology
Thyroid follicle
Functional unit
Lumen filled with colloid
Parafollicular cells (C cells)
Produce calcitonin
Physiology:
Function of thyroid gland
Produces T4-thyroxine, and active T3
Essential for normal growth, development, and metabolism
Produces calcitonin by thyroid C-cells
Calcium and phosphate homeostasis
Synthesis and secretion of thyroid hormones
S1: Trapping of iodide from blood into colloid (symporter used)
S2: Oxidation (iodide to iodine with TPO)
S3: Iodination (add iodine to TGB)
S4: Coupling
S5: Endocytosis (TGB into follicular cell)
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MIT + DIT = T3
DIT + DIT = T4
One iodine added to residue - Monoiodotyrosine (MIT)
2 iodines added - Diiodotyrosine (DIT)
Feedback loop of Thyroid gland
Hypothalamus release TRH
Anterioir pituitary release TSH
Stimulates thyroid gland, follicles release T3 and T4
T3 and T4 in blood increases
Homeostasis achieved
Inhibits secretion of TRH
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Investigations of thyroid disorders
Investigations
Blood tests
Thyroid function test
Serum free T4 and T3 concentration
High - hyperT
Low - hypoT
Serum TSH concentration
Low - hyperT
High - HypoT
Thyroid antibodies
Detect antibodies in autoimmune diseases
Anti-TSH receptor antibodies
Bind to TSH receptors stimulates thyroid hormone, leads to hyperthyroidism
Anty-thyroid peroxidase antibodies
Antibodies attack peroxidase, less hormones produced, hypothyroidism
Anti-Thyroglobulin antibodies
Antibodies target thyroglobulin, and the cells containing them, leading to hypothyroidism
Radiological tests
Ultrasound
Thyroid scintigraphy (RAIU)
Ingest smol amnt of radioactive iodine, see how much is absorbed by thyroid
Normal: 15-25%
Thyroid biopsy
Fine needle aspiration
Thin hollow needle extracts small tissue sample from thyroid nodule, sample checked under microscope for signs of cancer
Core needle biopsy
Same as FNA, but larger needle
Disorders
Functional
Hypothyroidism
Primary
Hashimoto's Thyroiditis
Autoimmune disorder, body attacks thyroid gland, causing damage and inflammation
Iodine deficiency
Congenital disorders
Secondary
Tumours
Trauma
Infiltrative disease
Surgery
Irradiation
Tertiary
Tumour
Trauma
Infiltrative disease
Iatrogenic
Surgical removal of thyroid glands
Radiation of neck
Drugs:
Lithium, Amiodarone
Thyroid gland does not make enough Thyroid hormone
Metabolism decreases
Hyperthyroidism
Primary
Grave's Disease
Autoimmune disorder, body produces Thyroid-stimulating immunoglobulins (TSI), mimics TSH
Symptoms
Exophthalmos (bulging eyes, often seen in Graves’ disease)
Hyperthyroidism symptoms
Toxic multinodular goitre
Nodules in thyroid gland secrete over excess hormones
Toxic Adenoma
Benign tumour secretes excess hormones
Secondary
TSH secreting pituitary adenoma
Tertiary
Rare tumour
Iatrogenic
Drugs:
Amiodarone, Levothyroxine
Thyroid gland makes too much Thyroid hormone
Metabolism increases
Symptoms
Weight loss despite increased appetite
Increased heart rate (tachycardia) and palpitations
Heat intolerance (feeling excessively warm)
Tremors (shaking hands or fingers)
Increased sweating
Nervousness, irritability, or anxiety
Frequent bowel movements and menstrual irregularities
Diagnosis
Thyroid function test: Low TSH, high T3/T4 levels
RAIU scan
Ultrasound
Fine needle aspiration
Can be:
Primary - Thyroid problem
Secondary - Pituitary problem
Tertiary - Hypothalamus problem
Iatrogenic
Thyroid enlargement
Malignant lesions
Papillary carcinoma
Follicular carcinoma
Medullary carcinoma
Anaplastic carcinoma
Benign lesions
Neoplastic
Nodular
Thyroid adenoma
Toxic adenoma
Abnormal growth of tissues
Non-neoplastic
Iodine deficiency
Inflammatory
Toxic
Physiological
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Diffuse
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Diffuse
Autoimmune - Hashimoto
Infective - Viral, bacterial
Diffuse/Nodular
Simple nontoxic goiter - Euthyroid
Goiter - HypoT
Toxic multinodular goiter - HyperT
No abnormal growth of tissues
Drugs used in thyroid disorders
HypoT drugs
T4 (Levothyroxine)
MOA
Standard replacement therapy
Start with low dose T4, buildup of 6-12 weeks
Reduce risk of developing HyperT
P kinetics
50-80% reabsorbed
Half life 6-8 days
Can treat cretinism also
T3 (Liothyronine)
P kinetics
More potent than T4
Short half life (<2days)
Deiodinated to inactive (rT3, T2, T1)
Cleared by hepatic clearance thru bile
Pregnancy increase dose (increased demand)
Menopause decrease dose (less oestrogen, low TBG, more free hormone)
Used for myxoedema coma
Adverse effects
Increased metabolism, potentiation
Overdose
HyperT symptoms
Myocardial ischaemia, arrythmia, heart failure
Treated with beta blocker
Iodine
MOA
Iodine used to make T3 and T4
HyperT drugs
Antithyroid drugs
Iodide
MOA
High doses inhibit T hormone secretion and synthesis
Wolff-Chaikoff effect
Oral prep: Lugol's iodine
Uses
Prep hyperT patients before thyroidectomoy
Thyroid storm
Radioactive Iodine
Best for nodular thyrotoxicosis
P kinetics
Single oral dose cures 80% of cases
Half life 8 days, effect within 1-2 mnths
50% risk of HypoT
Absolutely bad in pregnancy (women cannot conceive for 6mthns, meno cannot conceive for 4 mnths)
MOA
Patient emits B rays for 11-21 days
Rays cause cytotoxic action on thyroid follicles
B blockers
Nonselective B blocker
MOA
Inhibits peripheral conversion of T4 to T3???
Thionamides
MOA
Inhibit oxidation, organification, and coupling
PTU - inhibits peripheral conversion of T4 to T3
P kinetics
Carbimazole
Rapidly absorbed orally, converted to methimazole
Half life: 6-15hrs (depends on thyroid status)
Metabolised in thyroid and elsewhere
Excretion thru kidneys
Crosses placenta and breast milk
PTU
Shorter half life 2hrs
Protein bound
Crosses placenta and b milk less
preferred in pregnancy
Preferred in thyroid storm
Excreted in urine
Uses
Grave's disease (1-2 yrs of therapy, 50% long term remission)
Adverse effects
Hypothyroidism and goiter (long term use)
Agranulocytosis
Rash and pruritus
Fetal hypoT and goiter
Inhibit uptake of Iodide
Inhibit organification and hormone release
Inhibit peripheral thyroid hormone metabolism
Mood disorders
Classifications
Depressive ep
Def:
Decreased mood
ICD-11
Symptoms
Manic ep
Elevated mood
Mixed ep
Someone with BPD has both manic and depressive
Hypomanic ep
Less severe manic ep
Anxiety disorder