Ovarian follicles consist of an ovum and the surrounding follicular epithelial cells, also known as granulosa cells. In addition, the unit contains the connective tissue layers Theca interna and externa, which are summarized as Theca folliculi. Ripening ovarian follicles consist of correspondingly different types of cells.
One cell type of ovarian follicle is the so-called theca cell, as it is present in the theca folliculi and play a major role in the growth of the follicle. To be distinguished from the Theca cell is the thekalutein cell. These cells occur exclusively in the corpus luteum and develop from theca cells of the ovarian follicles. Counter cells are thus the precursor of the thekalutein cells. The luteinization in terms of the incorporation of lipids distinguishes more mature Thekaluteinzellen from conventional Theca cells.
Theca cells are a variant of connective tissue, as occurs only in the ovarian follicle. Histologically, motile and resident cells in extracellular collagen matrices or amorphous matrix form the connective tissue. Extracellular matrices form a three-dimensional meshwork with proteoglycans within the interstices.
The resilient cell-fiber framework makes connective tissue nearly resistant to tensile forces and the matrix distributes compressive forces. The Theca cells are differentiated connective tissue, which in the form of the Theca folliculi laps around the ovarian cortical zone (cortex ovarii) and envelops the ovarian follicle in the later stage of maturation. Unlike undifferentiated connective tissue, the specialized and differentiated Theca cells are capable of storing and producing substances. Thecalutein cells contain, for example, embedded lipids.
Theca cells take on different functions in the maturation of the ovarian follicle. They support the growth and final maturation of female follicles by expressing membrane-bound LH receptors. These receptors are 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 a sharp increase in secretion towards the middle of the cycle. This LH surge triggers ovulation, ovulation, and stimulates the synthesis of the corpus luteum. The binding of LH to the LH receptors within the Theca cells triggers the synthesis of steroids. More specifically, complex formation causes the production of testosterone. The testosterone is converted under the influence of FSH within the granulosa of the follicles in turn to the estrogen variant estradiol.
In addition, theca cells luteinize into thecalutein cells as found in the corpus luteum. The influence of LH causes hypertrophy in the Theca cells, which leads to the deposition of lipids and makes the Theca cells of the ovarian follicle to be the Theca cells of the corpus luteum. Basically, the formation of theca cells is associated with the development from the primary follicle to the secondary follicle.
The stage of the tertiary follicle causes in the cells a differentiation to functionally and histologically different cell layers. In this way, Theca interna and Theca externa of the ovarian follicle develop. The inner cell layer Theca interna, like the granulosa cells, is responsible for the estrogen synthesis in the follicle. The theca externa consists of contractile cells that expel the ovum from the mature follicle during ovulation.
Ovarian tumors are among the hormone-producing tumors and can take their origin in different tissue types of the ovary. In addition to granulosa cell tumors, for example, the cancer cell tumors exist. Mixed forms are referred to as granulosa theca cell tumors. Tumors from these tissues produce estrogens, as well as androgens, and are more prevalent in women between the ages of 50 and 60 years.
The mixed form of Granulosa cell and Theca cell tumors is also referred to as a luteinizing variant of ovarian tumors and is particularly evident in women between 20 and 30 years. The tissue type of the tumors allows a prognosis. Apparently the probability of malignancy is related to the cell type. For example, granulosa cell tumors are malignant in more than 50 percent of all cases. The cancer cell tumor, however, only with a probability of about twelve percent. Thus, pure theca cell tumors are in most cases benign tumors of the ovary.
The luteinized variant of granulosa theca cell tumors is, according to various sources, 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 mainly with the age of the patients. Postmenopausal women often experience bleeding as the first symptom. Pre-adolescent girls often develop an adolescent puberty praecox. This means that their sexual characteristics reach full education before puberty.
In some cases, the symptoms in this case also affect the skeleton. The development of symptoms for the theca cell tumor and the granulosa-theka cell variant mainly depends 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 concentration and can bring the entire organism out of balance.