Anatomy & Organs

Theca Cell – Structure, Function & Diseases

Theca cell

The theca cell is a type of connective tissue and is found in the ovarian follicle , where it plays important roles in follicle maturation. Under the influence of LH, the cells become thecal lutein cells, such as those found in the corpus luteum, by luteinization. Theca cell tumors and granulosa theca cell tumors are the best-known diseases of the tissue type and are among the hormone-producing tumors.

What is the theca cell?

Ovarian follicles consist of an oocyte and the surrounding follicular epithelial cells, also known as granulosa cells . The unit also contains the connective tissue layers Theca interna and externa, which are summarized as Theca folliculi. Maturing ovarian follicles consist of correspondingly different types of cells.

One cell type of the ovarian follicle is the so-called theca cell, which is present in the theca folliculi and plays a major role in the growth of the follicle. The thecal lutein cell is to be distinguished from the theca cell. These cells are found exclusively in the yellow body (corpus luteum) and develop from theca cells of the ovarian follicles. Theca cells are therefore the precursor of thecalutein cells. Luteinization, in the sense of storage of lipids , distinguishes mature theca-lutein cells from conventional theca cells.

Anatomy & Structure

Theca cells are a variant of connective tissue found only in the ovarian follicle. Histologically, motile and resident cells in extracellular collagen matrices or amorphous ground substance make up the connective tissue. Extracellular matrices form a three-dimensional meshwork with proteoglycans within the interstices.

The resilient cell-fiber structure makes connective tissue almost resistant to tensile forces and the basic substance distributes compressive forces. The theca cells are differentiated connective tissue which, in the form of theca folliculi, surrounds the ovarian cortical zone (cortex ovarii) and envelops the ovarian follicle in the later stage of maturity. Unlike undifferentiated connective tissue, the specialized and differentiated theca cells are able to store and produce substances. For example, thecalutein cells contain stored lipids.

Function & Tasks

Theca cells perform different functions in the maturation of the ovarian follicle. They support the growth and final maturation of female follicles by expressing membrane LH receptors. These receptors represent a binding site for the luteinizing hormone. The peptide is synthesized in the adenohypophysis and stimulates the secretion and synthesis of estrogens in the female gonads .

LH is a regulatory dominant factor in the second half of the female cycle. In the first half of the cycle, the hormone stimulates the synthesis of estrogens, with the release rising steeply towards the middle of the cycle. This LH surge triggers ovulation and stimulates the synthesis of the corpus luteum. With the binding of LH to the LH receptors within the theca cells, the synthesis of steroids is triggered. More specifically, the formation of the complex causes the production of testosterone. Under the influence of FSH, the testosterone is in turn converted to the estrogen variant estradiol within the granulosa cells of the follicles .

In addition, theca cells luteinize to form thecalutein cells found in the corpus luteum. Under the influence of LH, hypertrophy occurs in the theca cells, which leads to storage of lipids and transforms the theca cells of the ovarian follicle into theca-lutein cells of the corpus luteum. Basically, the formation of theca cells goes hand in hand with the development from the primary follicle to the secondary follicle.

The tertiary follicle stage causes the cells to differentiate into functionally and histologically different cell layers. In this way, theca interna and theca externa of the ovarian follicle develop. Like the granulosa cells, the inner cell layer Theca interna is responsible for estrogen synthesis in the follicle. The theca externa consists of contractile cells that expel the ovum from the mature follicle at ovulation .

Diseases

Ovarian tumors are among the hormone-producing tumors and can originate in different types of tissue in the ovary. In addition to granulosa cell tumors, there are, for example, theca cell tumors. Mixed forms are referred to as granulosa theca cell tumors. The tumors from these types of tissue produce estrogens and sometimes androgens and occur more frequently in women aged 50 to 60 years.

The mixed form of granulosa cell and theca cell tumors is also referred to as the luteinizing variant of ovarian tumors and is particularly evident in women between the ages of 20 and 30. The tissue type of the tumors allows a prognosis. It appears that the likelihood of malignancy is related to cell type. For example, granulosa cell tumors are malignant in up to more than 50 percent of all cases. Theca cell tumors, on the other hand, only have a probability of around twelve percent. Thus, in most cases, pure theca cell tumors are benign tumors of the ovary.

According to various sources, the luteinized variant of granulosa theca cell tumors is benign in almost all cases, whereas the conventional granulosa theca cell tumor is malignant with a probability of up to 27 percent. The symptoms of ovarian tumors from degenerated theca cells differ primarily with the age of the patient. Postmenopausal women often experience bleeding as the first symptom . Prepubescent girls often develop isosexual precocious puberty . This means that their sexual characteristics are fully developed before puberty.

In this case, the symptoms sometimes also affect the skeleton . For the theca cell tumor and the granulosa theca cell variant, the development of symptoms depends primarily on the hormones produced by the tumor and the extent of hormone production. In addition to estrogens and androgens, the tumors can also produce other hormones in individual cases , which are then detectable in increased concentrations and can throw the entire organism out of balance.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.