SUN-355 - Muscle Mayhem in Hypothyroidism

Hypothyroidism classically presents with cold intolerance, fatigue, fluid retention and dry
skin. Initial presentation can also include muscular involvement with exercise
intolerance, myalgias, cramping, stiffness and myoedema - a hypothyroid myopathy [1].
Cases where the muscular component of hypothyroidism is dominant may be more
challenging to identify as hypothyroidism. When undiagnosed and untreated,
hypothyroid myopathy can progress to more severe conditions including
rhabdomyolysis [1,2].
A 45 year old female with anxiety, depression, previous substance abuse, heart failure
and known fibroids presented to her primary care provider with severe muscle pain and
weakness in her lower back for the past month. She noted the muscle pain made it
difficult to sustain activity over 20 minutes. The pain in her lower back worsened and
was attributed to known fibroid or “general musculoskeletal pain.” As the condition
progressed over 2 months, the patient developed symptoms of brain fog, fatigue, water
retention and weight gain (totaling approximately 50 lbs over the past 9 months) on top
of the dominant myalgias and muscular symptoms. A laboratory evaluation of thyroid
function and creatine kinase (CK) revealed low free T4 (<0.1 ng/dL) and T3 (0.5 pg/mL)
with high TSH (78.00 μIU/mL) and thyroid peroxidase antibody (468 IU/mL) while CK
was 1567 U/L with 192 U/L as the upper limit of normal for CK. The patient was
diagnosed with rhabdomyolysis due to untreated severe Hashimoto's hypothyroidism.
She was treated with IV fluids and PO levothyroxine (200 μg/day) and within a week
myalgias improved and she was able to resume normal activities. The patient continued
oral levothyroxine and hydration and has returned to normal kidney function, thyroid
function and serum CK levels with abatement of myalgias.
This rhabdomyolysis due to Hashimoto's hypothyroidism is a rare presentation to
appreciate. This case highlights the importance of myalgias as an initial presentation for
hypothyroidism. It is of note that the patient had been taking rosuvastatin for at least 18
months prior to the onset of back pain. It has been documented that individuals with
untreated hypothyroidism, also taking statins for hypercholesterolemia, have developed
rhabdomyolysis [1,2]. Interestingly, whereas patients with hypercholesterolemia due to
hypothyroidism are often resistant to statins, this patient was managed by statins. This
case serves as a reminder of statin myotoxicity risk with undiagnosed hypothyroidism.
[1] Sindoni A, et al. Hypothyroid myopathy: A peculiar clinical presentation of thyroid
failure. Review of the literature. Rev Endocr Metab Disord. 2016;17(4):499-519.
[2] Chiang WF, et al. Case report: Rhabdomyolysis and kidney injury in a statin-treated
hypothyroid patient–kill two birds with one stone. Front Med. 2022;9.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*