Endocrinology

Missed Concepts

• During vitamin B12 repletion, you should monitor serum potassium, which can drop as new RBCs are formed.
• Prolactin-secreting pituitary adenomas, including large ones, are first treated with oral dopamine antagonists, whereas other pituitary adenomas are treated with surgery if large enough.
• Congenital Adrenal Hyperplasia is most commonly 21-hydroxylase deficiency (hypotension, low Na, high K, hypoglycemia, ambiguous genitalia in girls), but can also be 11β-hydroxylase deficiency (hypertension, low K, hypoglycemia, ambiguous genitalia in girls) or 17α-hydroxylase deficiency (hypertension, low K, euglycemia, ambiguous genitalia in boys).
• Discontinue metformin prior to surgeries with a high contrast load (e.g. cardiac cath)

Thyroid

• Workup of thyroid nodule almost always ends with FNA, the one exception is a patient without suspicious US findings or cancer risk factors, a low TSH, and a hot nodule on 123-Iodine scan (toxic adenoma). For these patients go straight to treatment (Methimazole pretreatment to achieve euthyroid > RF ablation vs. surgery)
• Hashimoto thyroiditis can be associated with other autoimmune conditions such as atrophic gastritis (pernicious anemia).
• Total T3 and T4 in pregnancy can be 1.5x normal range and still be physiologic. TSH is suppressed. There is no role for measuring free T4 in pregnancy
• Amiodarone decreases peripheral conversion of T4 to T3, but generally this self resolves in 6-9 months after treatment initiation. Amiodarone has a half-life of 100 days.
• Low T4 and low TSH suggests central hypothyroidism. Measure ACTH levels and get an ACTH stim test as well as AM serum cortisol.

Glucose Homeostasis

• One complication of SGLT2 inhibitors is euglycemic DKA with BG < 250, but still with an elevated AG and low pH.
• Hyperglycemia and catabolic symptoms (weight loss, urinary frequency) are indications for insulin.
• Young, normal weight patient, without family history of diabetes presents with symptomatic DKA? T1DM

Electrolyte Imbalanaces

Symptoms of Electrolyte Disturbances

Electrolyte	High	Low
Sodium	Example	Example
Potassium	Nausea, vomiting, ECG changes, asystole	Example
Calcium	Example	Usually asymptomatic, but can cause increased DTRs, muscle cramps, convulsions
Magnesium	Low-absent DTRs, flaccid paralysis, apnea	Example
Phosphorus	Example	Example

Hyponatremia

• Dx: Correct for Glucose. Moderate to severe hypothyroidism can cause cause mild euvolemic hyponatremia.

Hypercalcemia

• H&P:
• Dx: Best initial test is PTH
• Tx:

Hypocalcemia

• Dx: correct for albumin (Ca + 0.8*[4 - albumin])