RM, a 38-year-old woman who is attending graduate school and is very sedentary, comes to a community outpatient clinic. Her chief complaint is overwhelming fatigue that is not relieved by rest. She is so exhausted that she has difficulty walking to classes and trouble concentrating when studying. She reports a recent weight gain of 15 pounds (6.8 kg) over 2 months without clear changes in her dietary habits. Her face looks puffy, she has experienced excessive hair loss, and her skin is dry and pale. She says she has general body aches and pains with frequent muscle cramps and constipation. You note she is dressed inappropriately warmly for the weather. The physician orders lab work. The lab results are as follows:

WBC - WNL

HGB - WNL

Glucose - WNL

Amylase - WNL

Cholesterol - WNL

T4 (thyroxine) -↓

T3 (triiodothyronine) -↓

Thyroid-stimulating hormone (TSH) -↑

The physician diagnoses RM with an endocrine disorder. The assessment findings and lab work are consistent with which endocrine problem?

Choice A reason: Addison's Disease is characterized by insufficient production of adrenal hormones, leading to symptoms like weight loss, hyperpigmentation, low blood pressure, and severe fatigue. The lab findings would typically show low sodium, high potassium, and low cortisol levels. RM's lab results and symptoms are not consistent with Addison's Disease, making this an unlikely diagnosis.
Choice B reason: Cushing syndrome results from excess cortisol production, often causing weight gain, particularly around the abdomen and face, thinning skin, and hypertension. RM's symptoms of fatigue, dry skin, hair loss, and weight gain without dietary changes do not align with Cushing syndrome, and her lab results do not indicate elevated cortisol levels.
Choice C reason: Hyperthyroidism is characterized by excessive thyroid hormone production, leading to symptoms like weight loss, anxiety, palpitations, and heat intolerance. RM's symptoms of weight gain, fatigue, and cold intolerance, along with her lab results showing low T4 and T3 and elevated TSH, are not consistent with hyperthyroidism.
Choice D reason: Hypothyroidism occurs due to an underactive thyroid gland producing insufficient thyroid hormones. This leads to symptoms such as fatigue, weight gain, cold intolerance, dry skin, hair loss, and constipation. RM's lab results showing low T4 and T3 levels and elevated TSH align with the diagnosis of hypothyroidism. The body's response to low thyroid hormone levels is to increase TSH production in an attempt to stimulate the thyroid gland. The clinical presentation and lab findings point towards hypothyroidism as the correct diagnosis.