Case 29 Endocrinology

Hyperglycemia

Work it one clue at a time. The diagnosis stays hidden until you reveal it.

Clue 1

A 33 y/o F with carpal tunnel syndrome presents with polyuria and polydipsia. She has a fasting serum glucose of 212 mg/dL and a hemoglobin a1c of 9.7%.

Do you have an approach to hyperglycemia?

Clue 2

The first step is to determine whether we are dealing with insulin-dependent hyperglycemia or insulin-independent hyperglycemia.

Clue 3

Insulin-dependent hyperglycemia occurs as a result of insulin deficiency; insulin-independent hyperglycemia occurs despite the presence of insulin and is primarily the result of insulin resistance.

Clue 4

This can usually be determined clinically. When in doubt, obtaining simultaneous fasting plasma levels of glucose, insulin, and C-peptide can be informative. In the setting of hyperglycemia, insulin and C-peptide levels should be elevated; inappropriately low values are consistent with insulin deficiency (insulin-dependent hyperglycemia).

In this case, insulin and C-peptide are elevated.

Clue 5

It would be easy to call this type 2 DM and move on. The advanced clinician must consider secondary causes of insulin-dependent hyperglycemia. That’s why frameworks are so useful, even for a seemingly “every day” problems like hyperglycemia. The framework compels us to consider other possibilities.

Let’s revisit the photo at the start of the case.

Clue 6

What do you notice about the patient’s facial features compared to the driver license photo (taken 4 years prior)? Prominent facial features, most pronounced in the forehead (frontal bossing), nose, and lips, should generate a hypothesis.

With this hypothesis in mind you reach out and shake our patient’s hand. It feels moist and doughy. Here are the hands of a different patient with the same condition (courtesy @petesullivan):

Clue 7

With our hypothesis becoming more likely, we obtain retrospective history. The patient’s shoe size has increased over the years to the point where she can only fit into men’s shoes. Her ring size has doubled. She says her tongue has gotten larger and is difficult to move in her mouth.

We have all but made our diagnosis. Elevated serum levels of IGF-1 would be confirmatory.

Clue 8

Acromegaly is a rare condition that is caused by hypersecretion of GH and IGF-1, usually from a pituitary adenoma. Manifestations develop slowly over a period of years and vary depending on the levels of GH and IGF-1, patient age, tumor size, and the delay in diagnosis. Common features include headache, visual field deficits, acral and soft tissue overgrowth, macroglossia, macrognathia, arthralgias and arthritis, HTN, DM, sleep apnea, and carpal tunnel syndrome.

Viewing old photographs of a patient (eg, from a driver license) can be helpful in recognizing altered physical features caused by an underlying insidious disorder like acromegaly.

They will tell you physical exam doesn’t matter. They will also diagnose this patient with DM2. Don’t be like them.

End of case.