(12.08) A Near Miss: Acromegaly in a Patient with Anaphylaxis to Thyroid Hormone Replacement

Acromegaly results from the overproduction of growth (GH) and insulin-like growth factor 1 (IGF-1), usually from a sporadic, GH-secreting pituitary adenoma. At the time of diagnosis, greater than 70% are macroadenomas ( >10 mm) (1). The physical changes caused by this disorder are often initially subtle and insidious, and while the average age of diagnosis is from 40-50, this can be 5-10 years after symptom onset. Most patients who seek medical attention for acromegaly do so for its systemic manifestations or symptoms of tumor mass effect, with < 15% presenting for changing physical appearance (2).

Case(s) Description :

Our patient is a 60 year old female with a PMHx of obstructive sleep apnea and hypothyroidism (untreated x3 months while incarcerated) who presented with tongue swelling and shortness of breath after taking brand Tirosint. She was diagnosed with anaphylaxis, which responded to treatment with IV diphenhydramine and methylprednisolone. She had a significant history of anaphylactic reaction to brand and generic Synthroid, as well as baby aspirin, and as all of these have a yellow dye, this reaction was thought to be secondary to a dye allergy. Labs on admission were significant for TSH of 55 mIU/L and free T4 of 0.61 pmol/L, consistent with untreated hypothyroidism. She was started on IV levothyroxine and was transferred to the ICU for monitoring while dye-free levothyroxine 50 mcg tablets were trialed. A chest x-ray was concerning for thyromegaly. Follow-up CT neck showed marked thyromegaly and narrowing of the trachea. ENT recommended thyroidectomy once thyroid levels had stabilized. Though her acute dyspnea and lip swelling had improved, she did endorse several months of gradual neck swelling that had given her the sensation of orthopnea, despite using a CPAP. Additionally, she had a deepening voice, generalized weight gain, and swelling of her hands and feet during that time. Physical exam was consistent with macroglossia and jaw prognathism. Given the suspicion for acromegaly, an IGF-1 was checked and returned elevated at 789 nmol/L (normal < 186). The rest of her pituitary hormones were evaluated and were revealing only for a mildly elevated prolactin at 25 ng/mL (normal 4.8-23.3). An oral glucose tolerance test showed an initial GH level of 30 ng/mL that increased to 50 ng/mL after 2 hours, confirming the diagnosis. An MRI showed a 2.6 cm pituitary macroadenoma. Her treatment to date has included thyroidectomy by ENT and transsphenoidal resection of her macroadenoma by neurosurgery. The pathology showed a mixed somatotroph-lactotroph adenoma. Post-op GH < 1 ng/mL, suggesting chemical remission. She has been maintained on generic Levothyroxine 150 mcg (three 50 mcg dye-free tablets) for her thyroid replacement.

Discussion :

Acromegaly is a rare and often overlooked disease, with the “acromegalic window” spanning 5-10 years from symptom presentation to diagnosis. Given the benefit of early intervention in preventing the downstream effects of acromegaly, it is key for clinicians to know the signs and symptoms of acromegaly, so the presence of one or many will trigger a clinical suspicion for the disorder.