THYROID HORMONE RESISTANCE AND PERIODIC PARALYSIS—
QUESTION–I am looking for assistance with the following case: 18yo male with a diagnosis of thyroid hormone resistance made in childhood, though per the patient’s mother the disorder is reportedly not found in other family members
Most recent thyroid labs:
TSH 0.86 (0.35-4)
FT4 2.9 (0.8-1.5)
T3 287 (<210)
In addition he has multiple other abnormalities suggestive of a possible underlying genetic issue including microcephaly, thin corpus callosum, very mild intellectual disability, short metacarpals, short metatarsals, wide first toes, pectus carinatum, osteoporosis and undescended testis
In the last couple of months he has had two episodes of marked weakness. The one most recent and the only once documented by medical professionals occurred after the consumption of a high carbohydrate meal. He was so weak he was unable to walk and he had some vomiting. He was brought to the ER and was noted to be markedly hypokalemic with potassium level of 1.6. Phosphate level was 0.9 and Mg 1.3. His calcium was normal and his creatine kinase was elevated at 549 (<398). He recovered with electrolyte repletion. That was two weeks ago. There have not been additional episodes since that time, but the family is quite as anxious. As expected, he has no overt signs or symptoms of hyperthyroidism. HR is in the 50s. There is no goiter. There is no tremor.
Are patients with thyroid hormone resistance susceptible to thyrotoxic periodic paralysis or is this hypokalemic periodic paralysis separate entirely from the thyroid issue. Treatment?
Thank-you in advance for your assistance, Karen F Kartun, M.D. FACE Kaiser Permanente Fontana
RESPONSE-The thyroid function tests are suggestive of Resistant to Thyroid Hormone beta (RTHb). However, this diagnosis cannot be made without demonstration of a mutation in the THRB gene. The test is available in commercial laboratories, Quest being one of them. All somatic abnormality you describe have been reported in some individuals with RTHb but in less than 1% of cases indicating that theses are coincidental. Intellectual disability is common. Hypokalemic periodic paralysis has not been reported in more than 3000 cases of RTHb.
My laboratory will do the clinical and genetic testing as research at no cost but we require: (1) blood samples from all the family; as a minimum, patient, both parents and all sibling (2) the ethnic origin of the family (3) the reason the thyroid tests were obtained leading to the suspicion of RTHb (4) signatures on a consent form. Hope this helps, Samuel Refetoff, M.D.