is it genetically caused?
Genetic mutations in the L-type calcium channel α1-subunit have been described in Southern Chinese with TPP.
Thyrotoxic periodic paralysis
Genetic mutations in the L-type calcium channel α1-subunit (Ca1.1) have been described in Southern Chinese with TPP. The mutations are located in a different part of the gene from those described in the related condition familial periodic paralysis. In TPP, the mutations described are single-nucleotide polymorphisms located in the hormone response element responsive to thyroid hormone, implying that transcription of the gene and production of ion channels may be altered by increased thyroid hormone levels. Furthermore, mutations have been reported in the genes coding for potassium voltage-gated channel, Shaw-related subfamily, member 4 (K3.4) and sodium channel protein type 4 subunit alpha (Na1.4).

Of people with TPP, 33% from various populations were demonstrated to have mutations in "KCNJ18", the gene coding for K2.6, an inward-rectifier potassium ion channel. This gene, too, harbors a thyroid response element.
what is thyrotoxic periodic paralysis? It is a condition featuring attacks of muscle weakness in the presence of hyperthyroidism. what are the symptoms of it? An attack often begins with muscle pain, cramping, and stiffness. This is followed by weakness or paralysis.
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Thyrotoxic periodic paralysis [SEP] Genetics
Genetic mutations in the L-type calcium channel α1-subunit (Ca1.1) have been described in Southern Chinese with TPP. The mutations are located in a different part of the gene from those described in the related condition familial periodic paralysis. In TPP, the mutations described are single-nucleotide polymorphisms located in the hormone response element responsive to thyroid hormone, implying that transcription of the gene and production of ion channels may be altered by increased thyroid hormone levels. Furthermore, mutations have been reported in the genes coding for potassium voltage-gated channel, Shaw-related subfamily, member 4 (K3.4) and sodium channel protein type 4 subunit alpha (Na1.4).