A 29-year-old woman comes to the office due to increased hair loss. She delivered a healthy baby boy 8 months ago and has not felt the same since. The patient has fatigue and decreased libido, and her menstrual cycles have not returned. She has no prior medical problems and no drug allergies. The patient takes a multivitamin and does not use tobacco, alcohol, or illicit drugs. There is no significant family history. Blood pressure is 110/70 mm Hg and pulse is 58/min. Physical examination shows diffuse alopecia and thickened, brittle nails. The thyroid is nontender. Laboratory results show decreased serum TSH and free thyroxine (T4) levels. Which of the following is the most likely diagnosis in this patient?

Question

A 29-year-old woman comes to the office due to increased hair loss.  She delivered a healthy baby boy 8 months ago and has not felt the same since.  The patient has fatigue and decreased libido, and her menstrual cycles have not returned.  She has no prior medical problems and no drug allergies.  The patient takes a multivitamin and does not use tobacco, alcohol, or illicit drugs.  There is no significant family history.  Blood pressure is 110/70 mm Hg and pulse is 58/min.  Physical examination shows diffuse alopecia and thickened, brittle nails.  The thyroid is nontender.  Laboratory results show decreased serum TSH and free thyroxine (T4) levels.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec160b_3ac2_aa8d_9249_7f335084854b_MD0001_00 This patient has hypothyroidism manifesting as fatigue, hair loss, and brittle nails with a low serum thyroxine (T4) level. The low TSH confirms that this is due to hypothalamic-pituitary dysfunction (ie, central/secondary hypothyroidism) rather than a primary thyroid disorder, which would cause a compensatory rise in TSH. Central hypothyroidism is much less common than primary hypothyroidism. However, when it occurs, other hypothalamic-pituitary systems may be affected and patients may develop deficiencies of other pituitary hormones (eg, low gonadotropin levels leading to amenorrhea). The causes of central hypothyroidism are the same as those of hypopituitarism in general. Sheehan syndrome is ischemic necrosis of the pituitary gland and is typically caused by systemic hypotension during delivery. During pregnancy, the pituitary gland enlarges due to estrogen-induced hyperplasia of lactotrophs, but the blood supply does not increase proportionally. Subsequent peripartum hemorrhage with hypotension can cause underperfusion of the pituitary gland with subsequent ischemic injury. (Choices A and C) Chronic autoimmune (Hashimoto) thyroiditis is the most common cause of hypothyroidism. Postpartum thyroiditis is a variant of Hashimoto thyroiditis that occurs within a year of pregnancy. These disorders cause primary hypothyroidism with elevated TSH levels. (Choice B) Graves disease is an autoimmune disorder caused by activating antibodies against the TSH receptor. It presents with elevated T4 and suppressed TSH levels, typically with a goiter and ocular manifestations (eg, proptosis, lid lag). (Choice D) Secondary (central) hyperthyroidism is a rare disorder, usually caused by a TSH-secreting pituitary adenoma. Both TSH and serum T4 levels are elevated. (Choice F) Subacute granulomatous (de Quervain) thyroiditis causes a painful goiter and transient hyperthyroid symptoms; it typically follows a viral syndrome. Educational objective: Central hypothyroidism is characterized by low serum TSH and thyroxine (T4) levels and is due to hypothalamic-pituitary dysfunction. Sheehan syndrome is ischemic necrosis of the pituitary gland and is typically caused by systemic hypotension during delivery. In addition to central hypothyroidism, patients may also develop deficiencies of other pituitary hormones (eg, ACTH, prolactin, gonadotropins). __________ References: Clinical review: central hypothyroidism: pathogenic, diagnostic, and therapeutic challenges. (http://www.ncbi.nlm.nih.gov/pubmed/22851492)

A 29-Year-Old Woman Comes to the Office Due to Increased