Endocrine - Level 3 Flashcards
Physiology of PTH secretion?
o PTH secreted in response to low Ca2+ levels
o By 4 parathyroid glands situated posterior to thyroid
Control of PTH secretion?
o Negative feedback via Ca2+ levels
Actions of PTH?
o Increased osteoclast activity releasing Ca and PO4 from bones
o Increased Ca and decreased PO4 resorption in kidney
o Active 1, 25-dihydroxy-vitamin D production is increased
OVerall effect of PTH?
Raise Ca, lower PO4
Definition of hypoparathyroidism? - Congenital and Acquired?
- Hypoparathyroidism = low Ca, high PO4 and low (or inappropriately normal) PTH
o Congenital = gland failure, low secretion of PTH
o Acquired = Radiation, surgery (thyroidectomy, parathyroidectomy), hypomagnesaemia (Mg required for PTH secretion)
Definition of pseudo-hypoparathyroidism?
- Pseudohypoparathyroidism = low Ca, high PO4 with high PTH (PTH resistance)
Causes of congenital hypoparathyroidism?
Autoimmune destruction of glands – autoimmune polyglandular syndrome
• Type 1 – mutation of auto immuneregulator gene on c21
o Features: Addison’s, chronic candiasis, hypoparathyroidism, hypogonadism, pernicious anaemia, vitiligo, alopecia
• Type 2
o Features: Addison’s, T1DM, coeliac disease, hypothyroidism, hypogonadism, pernicious anaemia, vitiligo, alopecia
DiGeorge Syndrome
• CATCH22
• Cardiac defects, abnormal facies, thymic hypoplasia, cleft palate, hypocalcaemia c22q11 deletion
Kenny-Caffey syndrome, Kearns-Sayre syndrome, Sanjad-Sakati syndrome, Defect in calcium-sensing receptor gene/PTH gene
Causes of acquired hypoparathyroidism?
Post-neck surgery (thyroid, parathyroid, laryngeal, oesophageal)
Accidental damage, removal
Radiation
Chemotherapy
Alcohol
Infiltration of parathyroid glands (iron, copper)
Magnesium deficiency
Symptoms of hypocalcaemia?
- Muscle, bone and abdominal pain
SPASMODIC
o Spasms (carpopedal spasms = Trousseau’s sign)
o Perioral paraesthesia (face, fingers, toes)
o Anxious, irritable, irrational
o Seizures (grand mal)
o Muscle tone increased in smooth muscle (colic, wheeze, dysphagia)
o Orientation impaired (confused)
o Dermatitis
o Impetigo herpetiformis
o Chvotek’s sign (corner of mouth twitches when facial nerve tapped over parotid), cataract, cardiomyopathy
Blood tests performed in hypoparathyroidism? ECG findings in hypocalcaemia?
- Bloods o Bone profile – low Ca, high PO4, PTH PTH – low in primary and secondary PTH – high in pseudohypoparathyroidism o Serum Mg (may be low) o U&Es o Vitamin D levels o Others: TFTs, ACTH, Fe, Copper
- ECG
o Prolonged QT interval
Other investigations to consider in hypoparathyroidism?
o 24-hour urine calcium – usually low o Renal US o Brain MRI o Echocardiogram Cardiac abnormalities (DiGeorge)
Emergency treatment in hypoparathyroidism?
o If hypocalcaemia severe (<1.88mmol)
IV calcium gluconate (90mg) then infusion
Continuous ECG monitoring
o IF hypomagnesaemia
IV Magnesium sulphate 1g QDS
Acute asymptomatic or chronic treatment in hypoparathyroidism?
o Calcium and vitamin D supplements
Oral calcium carbonate 500-1000mg BDS/TDS
Oral calcitriol (vitD) 0.25-1mcg BDS
If inadequate – PTH hormone 50mcg SC OD
Thiazide diuretic reduces urinary calcium
o Magnesium supplements (if low)
Magnesium oxide 400mg oral BDS
Monitoring in hypoparathyroidism?
o Regular - serum Ca, albumin, phosphate and U&Es
o Urine calcium
o Renal imaging
Dietary advice in hypoparathyroidism?
o Rich in calcium and vitamin D
Complications in hypoparathyroidism?
o Laryngospasm o Muscle cramps, tetany, seizures o QT prolongation – syncope, arrhythmias o Renal stones o Stunted growth, malformed teeth
How common is thyroid cancer?
- Most common endocrine malignancy
- 1% of all malignancies
- Women
Risk factors of thyroid cancer?
o Exposure to ionising radiation (especially papillary) o History of thyroid goitre o Thyroid nodule o Thyroiditis o FHx of thyroid cancer o Females o Asians o Cowden’s syndrome o FAP
Types of thyroid cancer?
o Papillary (60%) o Follicular (25%) o Medullary (5%) o Anaplastic (5%) o Lymphoma (5%) o Hurthle Cell Carcinoma
Characteristics of papillary thyroid cancer?
Often younger patients 35-40
3x women
Spread – lymph nodes, lung (jugulo-diagastric node metastasis is called lateral aberrant thyroid)
Characteristics of follicular thyroid cancer?
Occur in middle age, 3x women
Well-differentiated
Spreads – early via blood (bone, lungs)
Characteristics of medullary thyroid cancer?
Parafollicular calcitonin-producing C cells of thyroid
Sporadic (80%) or part of MEN syndrome
May produce calcitonin
Do not concentrate iodine
Characteristics of anaplastic thyroid cancer?
From follicular cells but poor differentiation
Rare, elderly with poor response to treatment
Most aggressive cancer
Characteristics of lymphoma thyroid cancer?
Women more common
Mostly non-Hodgkins lymphoma
May present with dysphagia or stridor