<prompt> Cause of infertility in hypothyroidism...Decrease prolactinIncreasedprolactinBothNone  <response>: Ans. is b i.e., Increased prolactin Hypothyroidism is also linked to causing an excess release of the hormone prolactin. Prolactin is a hormone that stimulates the production of breast milk and an overproduction of this hormone can cause irregular periods and a halt in ovulation. 