Parathyroid Disorders - Hypo Flashcards
Hypocalcaemia, Hypomagnesemia, Pseudohypoparathyroidism
What is hypocalcaemia?
Low calcium levels in the blood serum
What are the most common causes of hypocalcaemia?
- Vitamin D deficiency
- Hypoparathyroidism
- Chronic kidney disease (CKD)
- Acute pancreatitis
- Rhabdomyolysis
What is pseudohypocalcaemia?
Apparent hypocalcaemia due to low albumin levels, as calcium is bound to albumin – corrected calcium must be calculated
What signs are seen in hypocalcaemia?
- Trousseau’s sign
(carpal spasm with BP cuff inflation) - Chvostek’s sign
(facial twitching when tapping facial nerve) - Hyperreflexia
- Prolonged QT interval on ECG
What ECG finding is associated with hypocalcaemia?
Prolonged QT interval
What blood test abnormalities indicate hypocalcaemia due to hypoparathyroidism?
- Low calcium
- low PTH
- normal/raised phosphate
How is acute severe hypocalcaemia managed?
(1) IV calcium gluconate
(10 mL of 10% solution over 10 minutes)
(2) followed by continuous IV infusion if needed
How is severe hypocalcaemia symptomatically defined?
Spasms
Long QT on ECG
Severe hypocalcaemia needs what first?
IV fluids/ replacements
A 60-year-old strict vegan visits his GP with tingling in his fingers and painful spasms of the hands and feet. The blood test shows a correct calcium 1.34 mmol/L (2.2-2.6). He is referred directly to the hospital.
What is an important test that must urgently be done?
ECG
A 37-year-old woman undergoes a thyroidectomy for resistant hyperthyroidism. 6 hours post-operatively the patient complains of tingling in the fingers, numbness around the mouth and hand spasms.
Which investigation findings are most associated with this presentation??
Prolonged QTc
A 58-year-old gentleman, recently diagnosed with Burkitt’s lymphoma, is about to start his first cycle of chemotherapy. The consultant-in-charge notifies the attending doctor and patient of the high possibility of tumour lysis syndrome.
Which electrolyte disturbance is most likely to be seen in this patient?
Hypocalcaemia
A 55-year-old gentleman presents to A&E with sudden-onset central abdominal pain radiating to his back, accompanied by nausea and vomiting. He reports a long history of significant alcohol intake, but otherwise has no significant past medical history. On examination, his ECG shows a prolonged QTc interval. During the triage assessment, the nurse inflates a blood pressure cuff on the patient’s arm, and notes that the patient develops involuntary muscle contractions in his hand.
What is the most appropriate management for the likely underlying electrolyte abnormality?
IV calcium gluconate
A 62-year-old woman with no past medical history presents with non-specific symptoms of mild nausea, fatigue and pain in her joints. The GP does a full workup and eventually diagnoses her with chronic kidney disease and hypocalcaemia. Her magnesium levels are noted to be normal. Apart from referring her to secondary care, the GP also prescribes her with calcium carbonate tablets and one additional supplement.
What is the most likely additional supplement to have been prescribed?
Calcitriol
A 45-year-old male patient presents with muscle cramps, numbness, and tingling sensation around the mouth, fingers, and toes. He has a background history of chronic renal failure.
Which is the most likely cause of his symptoms?
Hypocalcaemia
Hypomagnesemia
Low magnesium levels in the blood serum
How does magnesium deficiency affect calcium levels?
Magnesium is required for PTH release
Low Mg²⁺ → PTH inhibition → Secondary hypocalcaemia
Skeletal muscle receptors become less sensitive to PTH
What are the symptoms of hypomagnesaemia?
(1) Anorexia
(2) Nausea & vomiting
(3) Muscle weakness
(4) lethargy
(5) Seizures
What are the signs of hypomagnesaemia?
Cardiac arrhythmias
Positive Chvostek & Trousseau signs (due to secondary hypocalcaemia)
What blood tests should be done for suspected hypomagnesaemia?
Serum magnesium
Electrolytes (K⁺ and Ca²⁺)
What is the most dangerous cardiac complication of hypomagnesaemia?
Ventricular tachycardia
What are the causes of hypomagnesmia?
(1) Alcohol
(2) Drugs - thiazide, PPIs
(3) GI illness with diarrhoea
(4) Pancreatitis
(5) Malabsorption
A 38-year-old man with severe Crohn’s disease is started on total parental nutrition. Bloods on day 2 show a serum magnesium 0.12 mmol/L (0.7-1.0). Before he can be assessed, he collapses.
What is the most likely cause of his collapse?
Ventricular tachycardia
A 39-year-old male presents to his GP with general fatigue and weakness.
The GP decides to order some blood tests which show the following results:
Hb 126
MCV 92
WCC 6.5
platelets 203
Urea 7.1
creatinine 81
potassium 4.3
sodium 131
Magnesium 0.51
Vitamin D level 72
Based on these blood results, what finding is his ECG most likely to show?
Long QT interval
= The blood results show hypomagnesaemia which can cause a prolonged QT interval. It is one of the causes of Torsades de Pointes.
What is Pseudohypoparathyroidism?
Condition associated primarily with resistance to the parathyroid hormone
What is the primary cause of pseudohypoparathyroidism?
Genetic defect in the GNAS1 gene, leading to dysfunction of the Gs alpha subunit
What other factors can contribute to pseudohypoparathyroidism?
Trauma/iatrogenic
Autoimmunity
Low magnesium
What is the underlying mechanism of pseudohypoparathyroidism?
End-organ resistance to PTH due to a mutation in the Gs⍺-protein, which is coupled to the PTH receptor
What are the key clinical features of pseudohypoparathyroidism?
(1) Bone abnormalities
= McCune-Albright syndrome
(2) Obesity
(3) Subcutaneous calcification
(4) Learning disability
(5) Brachydactyly
= shortened 4th metacarpal
What are the characteristic blood findings in pseudohypoparathyroidism?
Low calcium
High PTH (due to resistance)
What is pseudo-pseudohypoparathyroidism?
A condition with the same phenotypic features as pseudohypoparathyroidism (Albright’s hereditary osteodystrophy) but without calcium abnormalities
What is a key difference between pseudohypoparathyroidism and pseudo-pseudohypoparathyroidism?
Pseudo-pseudohypoparathyroidism has normal calcium metabolism, while pseudohypoparathyroidism presents with low calcium and high PTH
A 15-year-old arrives at the Endocrine clinic. Routine blood tests show low calcium and high phosphate with high markedly raised parathyroid hormone. He has normal renal function. You also note they have blunting of the 4th and 5th knuckles.
What is the most likely diagnosis?
Pseudohypoparathyroidism
