Theca cells

The ceUular source of the various ovarian steroids has been difficult to unravel, but a transfer of substrates between two cell types is involved. Theca cells are the source of androstenedione and testosterone. These are converted by the aromatase enzyme in granulosa cells to estrone and estradiol, respectively. Progesterone, a precursor for all steroid hormones, is produced and secreted by the corpus luteum as an end-product hormone because these cells do not contain the enzymes necessary to convert progesterone ro other steroid hormones (Figure 42-8). 

Females, too, produce androgens, principally in the follicular theca cells. Androgens are also produced in the adrenals in both male and females. 

In the human female, IGF-1 is expressed by follicular theca cells, while IGF-2 is synthesized by granulosa cells (Chapter 8). The IGF-1 and -2 receptors are widely expressed in ovarian tissue, and synthesis of both growth factors and their receptors are influenced by circulating gonadotrophin levels. IGF-1 exerts a direct mitogenic effect on human granulosa cells, and promotes increased androgen and oestradiol synthesis by these cells. IGF-1 also promotes increased expression of FSH and LH receptors in ovarian tissue. 

Tajima, K., Yoshii, K., Fukuda, S., Orisaka, M., Miyamoto, K., Amsterdam, A., and Kotsuji, F. (2005). Luteinizing hormone-induced extracellular-signal regulated kinase activation differently modulates progesterone and androstenedione production in bovine theca cells. Endocrinology 146, 2903-2910. 

Theca lutein cysts are ovarian cysts that are lined by luteinized theca cells. They develop in patients with high levels of serum human chorionic gonadotropin. They are not as common as other ovarian cysts. They are associated with multiple gestations, trophoblastic disease, and pregnancies comphcated by hydrops fetalis, or in ovarian hyperstimulation syndrome. 

Sex cord stromal tumors include neoplasms that are composed of granulosa cells, theca cells, and their luteinized derivates, including Sertoli cells, Leydig cells, and fihrohlasts of gonadal stromal origin [37]. 

Cholesterol side-chain cleavage gene expression in theca cells augmented transcriptional regulation and mRNA stability in polycystic ova-rysyndrome. PLoS One 7 e48963... 

In an attempt to localize the target cells which are responsible for the concentration of HCG, autoradiography of histological sections was performed. It was found that the radioactivity was confined mainly to the follicular envelopes, theca cells, and also to the stroma. It seems that the density of black grains reflecting concentration of radioactivity was proportional to the state of follicular development. 

On the other hand the urinary excretion of 11-deoxy-17-ketosteroids was steadily increased in the patient in whom ovulation was not induced and in the ovary a marked hyperplasia of the theca cells was observed. 

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