A layer of cells around an ovarian follicle that produce androgens.
What theca cells are
Theca cells form the layer of cells wrapped around each small follicle in the ovary. A follicle is the tiny fluid-filled sac that holds a developing egg. Theca cells work in partnership with the granulosa cells that sit deeper inside, and the two share the job of building hormones. When stimulated by luteinising hormone (LH) from the pituitary gland, theca cells produce androgens such as testosterone. Those androgens then pass to the granulosa cells, which convert them into estrogen with the help of specific enzymes. In this way theca cells are the first step in the ovary’s chain for making sex hormones, and the balance between these two cell types matters for a healthy cycle.
How they relate to PCOS
In PCOS, theca cells often work harder than usual and overproduce androgens. Raised LH and insulin resistance can both encourage this, because excess insulin also stimulates the theca cells directly. When the hormone-making chain is disrupted, the egg inside a follicle may struggle to mature fully, which can affect ovulation. This is one of the biological reasons behind androgen signs such as acne, excess hair growth (hirsutism), oily skin, and irregular periods. For the wider picture, read what is PCOS and PCOS symptoms.
How their activity is assessed
Theca cells are not tested directly, because they sit deep within the ovary and cannot be reached by an ordinary blood test. Instead, a doctor judges the effect of their activity through blood androgen levels, such as testosterone, as part of a PCOS evaluation. Those results are read together with your cycle pattern, symptoms, and sometimes an ovarian scan, not on their own. One value alone does not tell the whole story. Because insulin resistance can add to the stimulation of theca cells, a plan discussed with a doctor sometimes also touches on metabolic health as well as androgen signs.
What it means for you
Understanding theca cells helps explain why androgen signs appear in PCOS, but it is not something you can measure yourself at home. If you have signs such as irregular periods or excess hair growth, a doctor can decide which tests are suitable and explain what the results mean in the context of your overall situation. Any decision about testing or treatment should be made with a doctor who knows your medical history.
This glossary is education, not diagnosis. For your own situation, ask a doctor or pharmacist.