Our continuing studies are directed: (1) to explore the nature of the defect in Isolated Gonadotropin Deficiency (IGD). To this end, we will examine the response of normals and of patients with IGD to 72-hour infusions of LHRH and establish the efficacy of long-term therapy with LHRH subcutaneously; (2) to examine the nature of the dopaminergic control of prolactin and TSH secretion in normals and in patients with IGD. We wish to establish whether this is secondary to deficiency of and reversible by estrogen; (3) to establish the nature of free alpha subunit by the JEG cell in vitro as a probe for studying this phenomenon in the human pituitary.