How is hypothyroidism differentiated from polycystic ovarian syndrome (PCOS)?

Updated: Sep 19, 2019
  • Author: Richard Scott Lucidi, MD, FACOG; Chief Editor: Richard Scott Lucidi, MD, FACOG  more...
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Thyroid dysfunction, rather than PCOS, may be the source of amenorrhea and hirsutism. (In patients with PCOS, thyroid function tests are within the reference range.)

Long-standing primary hypothyroidism can be associated with a markedly elevated circulating thyroid-stimulating hormone (TSH) level. Elevated alpha subunit delivery (from one half of the dimeric TSH molecule) can then cross-react with FSH and LH receptors on breast tissue, leading to premature thelarche and, on ovarian tissue, resulting in a PCOS–like picture. These physical findings of the van Wyk-Grumbach syndrome (ie, juvenile hypothyroidism, precocious puberty, and ovarian enlargement) resolve upon thyroxine replacement therapy.

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