IGF1 and vitamin D deficiency: This is consistent with the notion that efavirenz-induced vitamin D deficiency caused circulating IGF-1 deficiency in our cohort, as (1) efavirenz has been reported to induce vitamin D deficiency [39], (2) vitamin D is a known modulator of circulating IGF1 [38], and (3) efavirenz is the main NNRTI used by CHARTER subjects.