Different types of psoriasis, such as psoriasis vulgaris and erythrodermic psoriasis, are associated with varying thyroid hormone levels, with erythrodermic psoriasis patients showing normal levels of thyroid-stimulating hormone (TSH) and lower free triiodothyronine (FT3) or free thyroxine (FT4) levels. The gene discussed is TG; the disease is psoriasis.