Differential Diagnosis I
Thyroid Abnormalities
Systemic manifestations of hypothyroidism include multiple similarities with PCOS. Hypothyroidism may present with increased serum prolactin levels, increased estriol in women, anovulation, and menorrhagia (Thorton, et al., 2015). Weight gain and decreased glucose absorption can also be seen in both diagnoses. Evaluation includes laboratory testing of thyroid hormones. Hypothyroidism will be measured by an increased level of TSH alongside a decreased level of both total and free T3 as well as both total and free T4.
Hyperthyroidism generally occurs due to three different mechanisms. One being an exogenous source of thyroid hormone like an ovarian tumor (struma ovarii). Overlap in symptoms include menstrual irregularities. Weight gain is more commonly seen in PCOS. This overlap in both diagnoses can cause misdiagnosing. Looking superficially at lab values, a physician may see a decrease in TSH due to the increased negative feedback on the pituitary. Lab values may also show increase T4 and T3, giving the false appearance of hyperthyroid. By looking deeper into diagnostic testing and patient history the diagnosing physician would see a history of polycystic ovaries or undiagnosed PCOS symptoms.
Case Study Tip: CM presented to her PCP with complaints of significant weight gain (60 lbs). Weight gain can be seen in patients with PCOS as well as hypothyroidism.
Differential Diagnosis II
Cushing’s Syndrome 
(McCance & Huether, 2014)
Cushing’s syndrome is the overproduction of pituitary ACTH by a pituitary adenoma that can occur at any age (McCance & Huether, 2014). Clinical manifestation of Cushing’s that may mimic PCOS include weight gain with accumulation of adipose tissue in the trunk, face, and neck areas. Glucose intolerance also occurs in Cushing’s due to an increase in gluconeogenesis and glycogen storage in the liver. Glucose intolerance is common in PCOS as well. Patient’s experiencing Cushing’s may also experience increase in facial hair growth, acne, and oligomenorrhea which can all be seen in PCOS as well. When differentiating between Cushing’s and PCOS it is important to assess additional clinical manifestations of pituitary abnormalities that would not suggest PCOS. For example, persons experiencing Cushing’s syndrome experience a loss of protein matrix and an increase in bone resorption that can lead to osteoporosis, compression fractures of vertebrae, kyphosis, bone/back pain, and even decrease in overall height.
In order to rule out Cushing’s it may be necessary to test the patient’s urine over a 24-hour period. A free cortisol concentration that is higher than 50 mcg per 24 hours would indicate hypercortisolism not seen in patients with PCOS (McCance & Huether, 2014). Evaluating ACTH and cortisol levels in the blood can also help when differentiating diagnoses.
Case Study Tip: CM presented with significant weight gain which is seen in both diagnosis’. Despite not being diagnosed herself, CM has a family history of glucose intolerance which is another overlapping symptom seen in both diagnosis’.
Differential Diagnosis III
Hyperprolactinemia
Increased levels of prolactin cause many similar symptoms to PCOS. Women with hyperprolactinemia can experience menstrual irregularities and hirsutism also seen in PCOS. A major differentiating factor is galactorrhea (nonpuerperal milk production). Galactorrhea is not commonly seen in PCOS. Diagnostic testing may be necessary to rule out hyperprolactinemia from other causes, including blood testing for prolactin levels. Hyperprolactinemia may also be occurring due to other nonpituitary causes. Certain medications like tricyclic anti-depressants and antipsychotics like Risperidone can cause an increase in prolactin so taking a careful patient history is necessary for diagnosing. An MRI may be indicated to rule out hyperprolactinemia related to pituitary tumors.
Case Study Tip: Due to CM’s past medical history of abnormal bleeding, acne, and hirsutism it is important to rule out any abnormalities in the pituitary.