WBR0270

Author	[[PageAuthor::Gonzalo A. Romero, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology, MainCategory::Pathophysiology, MainCategory::Physiology
Sub Category	SubCategory::Endocrine
Prompt	[[Prompt::A 46-year-old woman presents to the outpatient rural clinic complaining of a 2-year history of constipation. She has taken over the counter fiber tablets which were not helping much. Her husband convinced her to go to the clinic after he entered the restroom and saw red bright blood in the toilet following the patient's defecation. She is allergic to penicillin, for which she had a severe allergic reaction 4 years ago. She stopped going to the doctor for a yearly checkup ever since; she is afraid of medications and their complications. She has a history of bilateral lower back abdominal pain radiated to the groin, which has resolved partially after taking lots of water; she states that "water is the best medicine". On review of systems she communicates that she has been feeling nauseated, urinating more than usual, has had bone and muscle aches. Upon physical examination she looks fatigued and her vitals are WNL. The mucous membranes are moist and without abnormalities. The neck is supple without any thyroid or lymph nodes enlargement, the rest of HEENT is normal. Lungs are clear to auscultation bilaterally without rales, wheezes or crackles. S1S2 RRR without murmurs, rubs or gallops. Abdomen is NT/ND, BS 3 per minute, CVA tenderness bilaterally, without organomegaly. Neuro is grossly intact. Her primary physician, which she has not seen in a long time, is thinking that a non-palpable benign tumor is most likely causing her symptoms. He decides to order a blood test to check for Calcium and PTH serum levels in order to confirm his suspicioun. Which of the following most likely correlates with this patient's serum findings? ]]
Answer A	AnswerA::A
Answer A Explanation	[[AnswerAExp::Incorrect. This represents the normal range of calcium and PTH values in serum; calcium levels vary from 8.5 to 10.2 mg/dL and PTH levels vary from 15-65 pg/mL. PTH increases when the ionized calcium level decreases.]]
Answer B	AnswerB::B
Answer B Explanation	[[AnswerBExp::Incorrect. Hypoparathyroidism can be caused by surgical removal of the parathyroids (i.e. thyroid surgery), or due to an autoinmune destruction of the glands. The lab values reveal low PTH and low calcium levels.]]
Answer C	AnswerC::C
Answer C Explanation	[[AnswerCExp::Incorrect. Secondary hyperparathyroidism is characterized by elevated PTH due to decreased levels of calcium. The most common causes are chronic renal insufficiency (due to impaired vitamin D hydroxylation towards its active form) and intestinal malabsorption of calcium.]]
Answer D	AnswerD::D
Answer D Explanation	[[AnswerDExp::Correct. Primary hyperparathyroidism can be caused by an adenoma, hyperplasia or carcinoma in the parathyroid glands. The increased levels of PTH increase the calcium levels above 10, therefore it corresponds to upper right corner on the graph.]]
Answer E	AnswerE::E
Answer E Explanation	[[AnswerEExp::Incorrect. This option corresponds to hypercalcemia independent of PTH, for example seen in metastatasis or excess calcium ingestion]]
Right Answer	RightAnswer::D
Explanation	[[Explanation::This patient is presenting with constipation, kidney stones, nausea, polydypsia, polyuria, muscle and bone pains, which is the typical presentation of primary hyperparathyroidism. The constipated habit of the patient made her bleed when defecating. Hyperparathyroidism courses with elevated PTH levels which increase the Calcium levels in blood. PTH has many functions: Increases bone resorption of both calcium and phosphate Increases renal reabsorption of calcium in the distal convoluted tubule Inhibits renal phosphate reabsorption Stimulates 1-alfa hydroxylase which converts Vit D 25-(OH) form into its active form (Vit D 1,25-0H or calcitriol) Calcium levels vary from 8.5 to 10.2 mg/dL and PTH levels vary from 15-65 pg/mL. Educational Objective: Hyperparathyroidism is frequently caused by a hyperfunctioning adenoma in a parathyroid gland PTH increases calcium and phosphorus serum levels Frequently it is asymptomatic, unless the calcium serum level is extremely high WikiDoc Mnemonics: Hyperparathyroidism causes stones, bones, and groans (kidney stones, bone pains and constipation). References: First Aid for STEP 1 2013, Endocrinology Chapter. Educational Objective: References: ]]
Approved	Approved::Yes
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