In humans, which glands produce chemicals that are distributed by the circulatory system and influence various target organs?

Human body has two types of glands : endocrine and exocrine.

The endocrine glands are ductless glands that secrete their hormones directly into the bloodstream. The hormones are chemical signals. The blood circulatory system then carries these chemical signals to target organs where their effects are seen.

Some examples of endocrine glands :

The pituitary gland secretes hormones and the hormones are carried by blood to various other glands (these are its target organs).

Diagram of pituitary gland and its various target organs :

The thyroid gland secretes thyroxin, a hormone which is carried to target organs (liver and other cells).

Insulin, a hormone secreted by a gland called pancreas into blood stream, is carried by blood to tissues (liver, kidney, brain, adipose tissue and other tissues) which are the target organs.

So, in short all endocrine glands produce chemicals that are distributed by the circulatory system and influence various target organs.