WBR0270

Author	PageAuthor::Gonzalo Romero
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 doctor 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, therefore she stopped going to the doctor for a yearly checkup. She is afraid of medications and their complications. She has a history of bilateral lower back pain abdominal pain radiated to the groin, and has resolved partially after taking lots of water; she states that "water is the best medicine". 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 w/o abnormalities. The neck is supple without any thyroid or lymph nodes enlargement, the rest of HEENT is normal. Lungs are CTA B/L w/o rales, wheezes or crackles. S1S1 RRR w/o murmur, rubs or gallops. Abdomen is NT/ND, BS negative, CVA tenderness bilaterally, w/o 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 drops.
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 Calcium levels, the left lower corner.
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. 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, like in metastatasis or excess calcium ingestion)
Right Answer	RightAnswer::D
Explanation	[[Explanation::This patient is presenting with constipation, kidney stones, nausea, polydypsia, 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 calcium and phosphate, increases renal reabsorption of calcium in the distal convoluted tubule, inhibits renal phosphate reabsorption and it stimulates 1 alfa hydroxylase which increases actice Vit D 1,25-(0H) vitamin D 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 the parathyroid glands. The increased levels of PTH increase Calcium and Phosporus levels. In rare ocasions the patient presents in symptoms, unless the calcium is extremely high. Educational Objective: References: ]]
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