claim: Doug Petrie was unable to appear in Dr. Horrible's Sing-Along Blog.
evidence: Pregnane is a C21 steroid and , indirectly , a parent of progesterone .. steroid. steroid. parent. Parent structure. progesterone. progesterone. It is a parent hydrocarbon for two series of steroids stemming from 5α-pregnane -LRB- originally allopregnane -RRB- and 5β-pregnane -LRB- 17β-ethyletiocholane -RRB- .. parent. Parent structure. hydrocarbon. hydrocarbon. 5β-pregnane. 5β-pregnane. It has a gonane core .. gonane. gonane. 5β-Pregnane is the parent of the progesterones , pregnane alcohols , ketones , and several adrenocortical hormones and is found largely in urine as a metabolic product of 5β-pregnane compounds .. parent. Parent structure. 5β-pregnane. 5β-pregnane. urine. urine. metabolic. metabolism