WBR0731

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Embryology
Sub Category	SubCategory::Endocrine
Prompt	[[Prompt::A 5 year old boy is brought by his mother to the physician's office for excessive urination. The mother also notes that her child is always complaining he has a dry mouth and is drinking water all the time. Upon further questioning, the physician notes that several members of the patient's extended family have a similar condition. The patient is found to be normoglycemic and has high-normal levels of plasma osmolality. Water restriction test is performed and shows an increase in urine osmolality to 1000 mOsmol/kg upon administration of antidiuretic hormone (ADH). Which of the following structures is derived from the same embyological origin as that responsible for the patient's condition?]]
Answer A	AnswerA::Retina
Answer A Explanation	AnswerAExp::Retina is derived from neuroectoderm.
Answer B	AnswerB::Dorsal root ganglia
Answer B Explanation	AnswerBExp::Dorsal root ganglia are derived from the neural crest.
Answer C	AnswerC::Schwann cells
Answer C Explanation	AnswerCExp::Schwann cells are derived from the neural crest.
Answer D	AnswerD::Parafollicular cells of the thyroid
Answer D Explanation	AnswerDExp::Parafollicular cells of the thyroid are derived from the neural crest.
Answer E	AnswerE::Follicular cells of the thyroid
Answer E Explanation	AnswerEExp::Follicular cells of the thyroid are derived from the endoderm.
Right Answer	RightAnswer::A
Explanation	[[Explanation::Central diabete insipidus may be familial is in the differential diagnosis of a very young patient presenting with polydipsia and polyuria. It is caused by the destruction of neurons of the supraoptic nucleus in the hypothalamus. As a result, ADH will not be produced by the hypothalamus and it will not be available for storage in the posterior pituitary. Water restriction test is an appropriate test to differentiate central vs. nephrogenic diabetes insipidus. In contrast to nephrogenic diabetes insipidus where ADH receptors are dysfunctional, the administration of ADH in central diabetes insipidus will cause remarkable elevation of urine osmolality, usually to more than 800 mOsm/kg. Both, the hypothalamus and the posterior pituitary are derived from the neuroectoderm. Educational Objective: Central diabetes insipidus is caused by the destruction of supraoptic nuclei of the hypothalamus, which is derived from the neuroectoderm. Retina is also derived from neuroectoderm. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::retina, WBRKeyword::neuroectoderm, WBRKeyword::embryological, WBRKeyword::origin, WBRKeyword::derived, WBRKeyword::central, WBRKeyword::diabetes, WBRKeyword::insipidus, WBRKeyword::polyuria, WBRKeyword::polydipsia, WBRKeyword::water, WBRKeyword::restriction, WBRKeyword::test, WBRKeyword::ADH, WBRKeyword::antidiuretic, WBRKeyword::hormone, WBRKeyword::hypothalamus, WBRKeyword::posterior, WBRKeyword::pituitary
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