URGE Written Exam Qs Flashcards
Janice is a 40-year-old woman who presents to her doctor complaining of palpitations and loss of weight despite good appetite. On questioning she described increasing intolerance to hot weather. Examination reveals that her pulse rate is 120 beats per min, and her blood pressure is 140/70 mmHg. Excessive retraction of the upper eyelid is noted and she has a fine tremor of the fingers. She also has a swelling at the front of the neck which you suspect may be an enlarged thyroid gland.
a) Describe the surface anatomy of the thyroid gland. (2 marks)
Blood tests reveal that she has a low concentration of thyroid stimulating hormone (TSH).
b) Explain the physiological mechanism underlying the low levels of TSH in this patient. (5 marks)
a) Two lateral lobes joined by an isthmus, lying in front of the larynx and trachea with isthmus (overlying the 2nd to 4th tracheal rings)
b) Hypothalamic TRH →pituitary TSH from pituitary→thyroid TSH receptor→synthesis of T3 and T4. T3 negative feed back on pituitary→decreased TSH secretion.
The low TSH levels suggest that the pathophysiology in this patient is excess thyroid hormone.
c) Describe how thyroid hormones interact with receptors on their target cells. (3 marks)
Thyroid hormones are lipophilic molecules and interact with intracellular hormone receptors. Hormone binding initiates protein synthesis following transcription of DNA and translation of mRNA.
Janice is a 40-year-old woman who presents to her doctor complaining of palpitations and loss of weight despite good appetite. On questioning she described increasing intolerance to hot weather. Examination reveals that her pulse rate is 120 beats per min, and her blood pressure is 140/70 mmHg. Excessive retraction of the upper eyelid is noted and she has a fine tremor of the fingers. She also has a swelling at the front of the neck which you suspect may be an enlarged thyroid gland.
Blood tests reveal that she has a low concentration of thyroid stimulating hormone (TSH).
d) Name three (3) possible pathological causes of this patient’s symptoms. Include in your answer an explanation of which you think is most likely in this patient. (4 marks)
- Any three of the following Graves disease, toxic multimodular goitre
- solitary toxic nodule/adenoma or less likely acute thyroiditis, gestational thyrotoxicosis,
- exogenous iodine, drugs, thyrotoxicosis factitia, rarely TSH secreting tumours, thyroid carcinoma
Most likely diagnosis : Graves: most common cause and the eye signs only occur in Graves disease.
Janice is a 40-year-old woman who presents to her doctor complaining of palpitations and loss of weight despite good appetite. On questioning she described increasing intolerance to hot weather. Examination reveals that her pulse rate is 120 beats per min, and her blood pressure is 140/70 mmHg. Excessive retraction of the upper eyelid is noted and she has a fine tremor of the fingers. She also has a swelling at the front of the neck which you suspect may be an enlarged thyroid gland.
Blood tests reveal that she has a low concentration of thyroid stimulating hormone (TSH).
e) Janice’s symptoms could also be explained by an anxiety disorder. What features of her presentation make anxiety a less likely cause of her signs and symptoms? (2 marks)
f) Globally, dietary iodine deficiency is a major cause of thyroid disease. Briefly describe why iodine is an essential requirement for normal thyroid function. (4 marks)
e) Her changed heart rate and palpitations could be due to anxiety however her upper eyelid retraction and the neck swelling, loss of weight despite good appetite are suggestive of thyroid disorder. Decreased TSH would also not be low with anxiety.
f) Iodine is needed for the synthesis of thyroxine in the follicles of thyroid gland. Iodine is taken up by follicular cells in the form of iodide by a specific Na+/I- cotransporter, is oxidised to iodine in the follicle lumen and then incorporated into tyrosine to form mono-iodotyrosine and di-iodotyrosine bound to thyroglobulin. Iodotyrosines are conjugated to form T3 and T4 on the thyroglobulin, which is secreted into the colloid where T3 & T4 are cleaved off and released All of these actions are stimulated by TSH and the conjugation step does not take place if the tyrosine molecules are not iodinated. Lack of dietary iodine leads to hypothyroidism and associated signs and symptoms. Lack of iodine will lead to lack of thyroid hormones and will prevent the negative feedback that normally stops continuous stimulation of the thyroid gland producing excessive thyroglobulin.
Maria is a 65-year-old woman who presents with blood pressure of 162/100 mmHg and peripheral oedema.
a) Describe the effects of each listed class of drug on kidney function. (3 marks)
Loop diuretic e.g. frusemide
Increased excretion of Na in the thick ascending loop of Henle. Inhibition the Na/K/Cl co-transporter to decrease re-absorption of Na and subsequently increasing loss of K.
Thiazide diuretic e.g.
hydrochlorothiazide Inhibition of the Na/Cl co-transporter located in the distal tubule causing the loss of Na and Cl.
Aldosterone inhibitor e.g. spirolactone
Inhibition distal sodium reabsorbtion and K secretion but have limited effects on the kidney.
Maria is a 65-year-old woman who presents with blood pressure of 162/100 mmHg and peripheral oedema.
b) What are the two main determinants of mean arterial pressure? (1 mark)
c) Describe how diuretics and ACE inhibitors affect the determinants of mean arterial pressure in a patient with normal heart function. (4 marks)
b) Mean arterial pressure = cardiac output x peripheral resistance
c) Diuretics
Diuretics decrease cardiac output by lowering plasma volume due to decreased reabsorption of salts
ACE inhibitors
Inhibit angiotensin II (AngII) production.
Decrease peripheral resistance by inhibiting AngII mediated contraction of vascular smooth muscle.
Decrease cardiac output by:
- inhibiting AngII mediated aldosterone secretion (inhibit aldosterone mediated fluid retention)
- inhibiting AngII mediated stimulation of hypothalamic release of vasopressin ((AVP) antidiuretic hormone (ADH)) (inhibit ADH mediated fluid retention)
Maria is a 65-year-old woman who presents with blood pressure of 162/100 mmHg and peripheral oedema.
The elevated creatinine level indicates that there has been less filtered through the kidneys. Creatinine clearance and plasma creatinine levels can be used as an indirect measure of GFR since creatinine is usually 100% filtered by the kidneys and not reabsorbed at all (but a small amount is secreted into the urine). The elevated plasma creatinine indicates reduced urinary excretion of creatinine and thus estimates a reduced GFR which is indicated in the UEC results and confirms a reduction in kidney filtration and function.
e) Outline the processes involved in the transport of Na+, K+ and Glucose components of the kidney filtrate across the cells of the nephron. For each component, also provide the net result of the passage of the filtrate through the kidney (e.g. net reabsorption or net excretion). (6 marks)
Na+
Transport processes: Kidney filtrate is high in Na+ so it diffuses across the apical cell surface and is then actively pumped out the basal cell surface by the Na+/K+-
ATPase
Result: Reabsorption
- *K+**
- *Transport processes:** K+ is freely filtered in the glomerulus, passively reabsorbed down its concentration gradient back into the bloodstream, then actively excreted ) into the filtrate in 2 steps: Na+/K+-ATPase across basal cell surface into the tubular cells and then passive diffusion into the tubule lumen (i.e. urine) through the apical membrane
- *Result:** Excretion
- *Glucose**
- *Transport processes:** Glucose is freely filtered in the glomerulus and reabsorbed by secondary active transport, following sodium reabsorption.
- *Result:** Reabsorption
f) How is an acidic load buffered by the kidney? (2 marks)
The main buffers within the kidney filtrate are phosphate ions and urea.
Phosphate ions buffer as follows: H2PO−4 ⇋ H+ + HPO2−4
Urea buffer as it contains acidic & basic elements e.g. COO- is basic & the NH3+ is acidic
-COO- + H+ ⇋ ‐COOH
‐NH3++ OH‐ ⇋ ‐NH2 + H2O
The doctor performs urinalysis and based on the results suspects nephrotic syndrome.
g) Give two clinical features of this syndrome and one possible cause. (3 marks)
Features: any two of protein in urine, oedema, high cholesterol
Possible cause: any one of the following: glomerulonephritis, diabetes, basement membrane disease, SLE
