Yes, both testes and penis growth along with all aspects of pubertal growth in boys depends on testosterone also, but it depends on how low is 'low' you are talking about. Though the reference level of testo varies some what from lab to lab, here is a link from Mayo Clinic giving their standard levels up to adult age. If you are within the range limits specified there for your age then, you may need not have to worry, if not better to consult an Endocrinologist. Also, when you say penis growth, there is a large possible variation and individual perception can differ. So if you have any doubts, better to consult a urologist.
Sorry, here is the link I was referring to :