Gland that is located in the neck, butterfly-shaped with two lobes united by a narrow isthmus. Highly vascular
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Parafollicular
Also known as C cells - minority of the thyroid cells, secretes calcitonin to decrease calcium concentration (inhibits osteoclasts from breaking down bone). Not essential to life as other tissues also secrete calcitonin
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Follicular epithelial
Make up majority of the thyroid cells - line the spherical follicles and surround the lumen filled with colloid (thyroid hormone store). Responsive to TSH
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Iodine
Sources: fish, seaweed, crops, etc. Can also be fortified from dairy. Transported into follicular cells against concentration gradient using NIS then into follicular lumen passively
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NIS
Sodium-iodide symporter, located on basolateral membrane. Na+/K+ATPase creates low concentration of Na+ in the cell. Acts as a cotransporter, transports Na+ along gradient and I- against gradient
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Pendrin
An anion transporter, located on the apical membrane of follicular cells which aids the movement of I- from the cell to the follicular lumen (site of thyroid hormone synthesis)
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Thyroglobulin
A glycoprotein dimer with tyrosine residues which acts as the scaffold for thyroid hormone synthesis
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Thyroid peroxidase
An enzyme located on the apical membrane which catalyses: oxidation of iodide to faciliate iodination of Tg and the coupling of iodotyrosines to form thyroid hormone
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Triiodothyronine
T3: Monoiodotyrosine + diiodotyrosine. Biologically active hormone
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Thyroxine
T4: two diiodotyrosines. Prohormone
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MCT8
Thyroid hormone transporter which secretes T3 and T4 into the bloodstream and can also re-uptake them into tissues
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TSHR
The GPCR which (when TSH binds), causes a conformational change, replacing the alpha subunits GDP with active GTP, releasing the subunit to activate adenylyl cyclase which converts ATP to cAMP. This causes release of PKA
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Protein kinase A
Activated form can phosphorylate transcription factors like CREB which induces transcription of thyroid specific genes, like Tg and NIS
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Alpha I
A receptor gene distributed in heart and muscle
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Alpha II
A receptor gene which binds to response elements of genes; may suppress
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Beta I
A receptor gene distributed in the liver, kidney, brain and pituitary
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Beta II
A receptor gene distributed in pituitary and CNS (negative feedback)
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TSH
Hormone which stimulates expression of NIS, Tg and TPO. Stimulates the plasma membrane localisation of NIS and pendrin transport. Stimulates the endocytosis of thyroid hormone when needed
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TBG
Thyroxine binding globulin - 70% thyroid hormone bound as they are highly lipophilic. Less than 1% free
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Deiodinase II
Converts T4 into active T3 by removing iodine from outer ring
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Deiodinase III
Converts T4 into inactive rT3 by removing iodine from inner ring
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Deiodinase I
Can remove iodine from outer or inner ring of T4
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Thyroid hormone
Hormone that acts on almost all tissues. It is essential for early brain development, skeletal maturation, increases basic metabolic rate, increases carbohydrate/fat metabolism. Increases cholesterol secretion in bile to remove circulating cholestero
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Hyperthyroidism
Low TSH, high T3 and T4 levels. Overactive thyroid. Symptoms: rapid heart rate, shortness of breath, weight loss, diarrhoea, increased appetite, tremor, anxiety, double vision
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Grave's disease
Autoimmune disease where pathogenic antibodies continually stimulate TSH receptors, raising T3 and T4. Symptoms: goitre, bulging eyes. Treated with carbimazole (anti-thyroid), surgery, radioactive iodine
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Hypothyroidism
High TSH, low T3 and T4. Underactive thyroid. Symptoms: slow heart rate, weight gain, constipation, rash on legs, vitiligo, depression, carpal tunnel
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Hashimoto's thyroiditis
Autoimmune disease where antibodies have an antagonistic effect on TPO and Tg, causing destructing of follicles. Iodine deficiency causing goitre enlargement for compensation,. Treatment: levothyroxine
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Other cards in this set
Card 2
Front
Also known as C cells - minority of the thyroid cells, secretes calcitonin to decrease calcium concentration (inhibits osteoclasts from breaking down bone). Not essential to life as other tissues also secrete calcitonin
Back
Parafollicular
Card 3
Front
Make up majority of the thyroid cells - line the spherical follicles and surround the lumen filled with colloid (thyroid hormone store). Responsive to TSH
Back
Card 4
Front
Sources: fish, seaweed, crops, etc. Can also be fortified from dairy. Transported into follicular cells against concentration gradient using NIS then into follicular lumen passively
Back
Card 5
Front
Sodium-iodide symporter, located on basolateral membrane. Na+/K+ATPase creates low concentration of Na+ in the cell. Acts as a cotransporter, transports Na+ along gradient and I- against gradient
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